Input File Description

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Input File Description Program: pw.x / PWscf / Quantum Espresso TABLE OF CONTENTS INTRODUCTION &CONTROL calculation | title | verbosity | restart_mode | wf_collect | nstep | iprint | tstress | tprnfor | dt | outdir | wfcdir | prefix | lkpoint_dir | max_seconds | etot_conv_thr | forc_conv_thr | disk_io | pseudo_dir | tefield | dipfield | lelfield | nberrycyc | lorbm | lberry | gdir | nppstr | lfcpopt &SYSTEM ibrav | celldm | A | B | C | cosAB | cosAC | cosBC | nat | ntyp | nbnd | tot_charge | tot_magnetization | starting_magnetization | ecutwfc | ecutrho | ecutfock | nr1 | nr2 | nr3 | nr1s | nr2s | nr3s | nosym | nosym_evc | noinv | no_t_rev | force_symmorphic | use_all_frac | occupations | one_atom_occupations | starting_spin_angle | degauss | smearing | nspin | noncolin | ecfixed | qcutz | q2sigma | input_dft | exx_fraction | screening_parameter | exxdiv_treatment | x_gamma_extrapolation | ecutvcut | nqx1 | nqx2 | nqx3 | lda_plus_u | lda_plus_u_kind | Hubbard_U | Hubbard_J0 | Hubbard_alpha | Hubbard_beta | Hubbard_J(i,ityp) | starting_ns_eigenvalue(m,ispin,I) | U_projection_type | edir | emaxpos | eopreg | eamp | angle1 | angle2 | constrained_magnetization | fixed_magnetization | lambda | report | lspinorb | assume_isolated | esm_bc | esm_w | esm_efield | esm_nfit | fcp_mu | vdw_corr | london | london_s6 | london_c6 | london_rcut | xdm | xdm_a1 | xdm_a2 | space_group | uniqueb | origin_choice | rhombohedral &ELECTRONS electron_maxstep | scf_must_converge | conv_thr | adaptive_thr | conv_thr_init | conv_thr_multi | mixing_mode | mixing_beta | mixing_ndim | mixing_fixed_ns | diagonalization | ortho_para | diago_thr_init | diago_cg_maxiter | diago_david_ndim | diago_full_acc | efield | efield_cart | startingpot | startingwfc | tqr &IONS ion_dynamics | ion_positions | pot_extrapolation | wfc_extrapolation | remove_rigid_rot | ion_temperature | tempw | tolp | delta_t | nraise | refold_pos | upscale | bfgs_ndim | trust_radius_max | trust_radius_min | trust_radius_ini | w_1 | w_2 &CELL cell_dynamics | press | wmass | cell_factor | press_conv_thr | cell_dofree ATOMIC_SPECIES X | Mass_X | PseudoPot_X ATOMIC_POSITIONS X | x | y | z | if_pos(1) | if_pos(2) | if_pos(3) K_POINTS nks | xk_x | xk_y | xk_z | wk | nk1 | nk2 | nk3 | sk1 | sk2 | sk3 CELL_PARAMETERS v1 | v2 | v3 CONSTRAINTS nconstr | constr_tol | constr_type | constr(1) | constr(2) | constr(3) | constr(4) | constr_target OCCUPATIONS f_inp1 | f_inp2 ATOMIC_FORCES X | fx | fy | fz

INTRODUCTION Input data format: { } = optional, [ ] = it depends, | = or All quantities whose dimensions are not explicitly specified are in RYDBERG ATOMIC UNITS. Charge is "number" charge (i.e. not multiplied

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by e); potentials are in energy units (i.e. they are multiplied by e) BEWARE: TABS, DOS CHARACTERS ARE POTENTIAL SOURCES OF TROUBLE Comment lines in namelists can be introduced by a "!", exactly as in fortran code. Comments lines in ``cards'' can be introduced by either a "!" or a "#" character in the first position of a line. Do not start any line in ``cards'' with a "/" character. Structure of the input data: =============================================================================== &CONTROL ... / &SYSTEM ... / &ELECTRONS ... / [ &IONS ... / ] [ &CELL ... / ] ATOMIC_SPECIES X Mass_X PseudoPot_X Y Mass_Y PseudoPot_Y Z Mass_Z PseudoPot_Z ATOMIC_POSITIONS { alat | bohr | crystal | angstrom | crystal_sg } X 0.0 0.0 0.0 {if_pos(1) if_pos(2) if_pos(3)} Y 0.5 0.0 0.0 Z O.0 0.2 0.2 K_POINTS { tpiba | automatic | crystal | gamma | tpiba_b | crystal_b | tpiba_c | crystal_c } if (gamma) nothing to read if (automatic) nk1, nk2, nk3, k1, k2, k3 if (not automatic) nks xk_x, xk_y, xk_z, wk [ CELL_PARAMETERS { alat | bohr | angstrom } v1(1) v1(2) v1(3) v2(1) v2(2) v2(3) v3(1) v3(2) v3(3) ] [ OCCUPATIONS f_inp1(1) f_inp1(11) [ f_inp2(1) f_inp2(11)

f_inp1(2) f_inp1(12) f_inp2(2) f_inp2(12)

f_inp1(3) ... f_inp1(10) ... f_inp1(nbnd) f_inp2(3) ... f_inp2(10) ... f_inp2(nbnd) ] ]

[ CONSTRAINTS nconstr { constr_tol } constr_type(.) constr(1,.)

constr(2,.) [ constr(3,.)

constr(4,.) ] { constr_target(.) } ]

[ ATOMIC_FORCES label_1 Fx(1) Fy(1) Fz(1) ..... label_n Fx(n) Fy(n) Fz(n) ]

Namelist: CONTROL calculation Default:

CHARACTER 'scf'

a string describing the task to be performed: 'scf', 'nscf', 'bands', 'relax', 'md', 'vc-relax', 'vc-md'

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(vc = variable-cell).

[Back to Top] title

CHARACTER Default:

''

reprinted on output.

[Back to Top] verbosity

CHARACTER

Default:

'low'

Currently two verbosity levels are implemented: 'high' and 'low'. 'debug' and 'medium' have the same effect as 'high'; 'default' and 'minimal', as 'low'

[Back to Top] restart_mode Default: 'from_scratch' 'restart'

CHARACTER 'from_scratch' : from scratch. This is the normal way to perform a PWscf calculation : from previous interrupted run. Use this switch only if you want to continue an interrupted calculation, not to start a new one, or to perform non-scf calculations. Works only if the calculation was cleanly stopped using variable "max_seconds", or by user request with an "exit file" (i.e.: create a file "prefix".EXIT, in directory "outdir"; see variables "prefix", "outdir"). Overrides "startingwfc" and "startingpot".

[Back to Top] wf_collect

LOGICAL

Default:

.FALSE.

This flag controls the way wavefunctions are stored to disk : .TRUE.

collect wavefunctions from all processors, store them into the output data directory "outdir"/"prefix".save, one wavefunction per k-point in subdirs K000001/, K000001/, etc.. Use this if you want wavefunctions to be readable on a different number of processors.

.FALSE. do not collect wavefunctions, leave them in temporary local files (one per processor). The resulting format will be readable only by jobs running on the same number of processors and pools. Requires less I/O than the previous case. Note that this flag has no effect on reading, only on writing.

[Back to Top] nstep

INTEGER Default:

1 if calculation = 'scf', 'nscf', 'bands'; 50 for the other cases

number of ionic + electronic steps

[Back to Top] iprint

INTEGER Default:

write only at convergence

band energies are written every "iprint" iterations

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[Back to Top] tstress

LOGICAL Default:

.false.

calculate stress. It is set to .TRUE. automatically if calculation='vc-md' or 'vc-relax'

[Back to Top] tprnfor

LOGICAL

calculate forces. It is set to .TRUE. automatically if calculation='relax','md','vc-md'

[Back to Top] dt

REAL Default:

20.D0

time step for molecular dynamics, in Rydberg atomic units (1 a.u.=4.8378 * 10^-17 s : beware, the CP code uses Hartree atomic units, half that much!!!)

[Back to Top] outdir

CHARACTER Default:

value of the ESPRESSO_TMPDIR environment variable if set; current directory ('./') otherwise

input, temporary, output files are found in this directory, see also "wfcdir"

[Back to Top] wfcdir

CHARACTER Default:

same as "outdir"

this directory specifies where to store files generated by each processor (*.wfc{N}, *.igk{N}, etc.). Useful for machines without a parallel file system: set "wfcdir" to a local file system, while "outdir" should be a parallel or networkfile system, visible to all processors. Beware: in order to restart from interrupted runs, or to perform further calculations using the produced data files, you may need to copy files to "outdir". Works only for pw.x.

[Back to Top] prefix

CHARACTER Default:

'pwscf'

prepended to input/output filenames: prefix.wfc, prefix.rho, etc.

[Back to Top] lkpoint_dir Default:

LOGICAL .true.

If .false. a subdirectory for each k_point is not opened in the "prefix".save directory; Kohn-Sham eigenvalues are stored instead in a single file for all k-points. Currently doesn't work together with "wf_collect"

[Back to Top] max_seconds Default:

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REAL 1.D+7, or 150 days, i.e. no time limit



jobs stops after "max_seconds" CPU time. Use this option in conjunction with option "restart_mode" if you need to split a job too long to complete into shorter jobs that fit into your batch queues.

[Back to Top] etot_conv_thr Default:

REAL 1.0D-4

convergence threshold on total energy (a.u) for ionic minimization: the convergence criterion is satisfied when the total energy changes less than "etot_conv_thr" between two consecutive scf steps. Note that "etot_conv_thr" is extensive, like the total energy. See also "forc_conv_thr" - both criteria must be satisfied

[Back to Top] forc_conv_thr Default:

REAL 1.0D-3

convergence threshold on forces (a.u) for ionic minimization: the convergence criterion is satisfied when all components of all forces are smaller than "forc_conv_thr". See also "etot_conv_thr" - both criteria must be satisfied

[Back to Top] disk_io

CHARACTER Default:

see below

Specifies the amount of disk I/O activity 'high': save all data to disk at each SCF step 'medium': save wavefunctions at each SCF step unless there is a single k-point per process (in which case the behavior is the same as 'low') 'low' :

store wfc in memory, save only at the end

'none':

do not save anything, not even at the end ('scf', 'nscf', 'bands' calculations; some data may be written anyway for other calculations)

Default is 'low' for the scf case, 'medium' otherwise. Note that the needed RAM increases as disk I/O decreases! It is no longer needed to specify 'high' in order to be able to restart from an interrupted calculation (see "restart_mode") but you cannot restart in disk_io='none'

[Back to Top] pseudo_dir Default:

CHARACTER value of the $ESPRESSO_PSEUDO environment variable if set; '$HOME/espresso/pseudo/' otherwise

directory containing pseudopotential files

[Back to Top] tefield

LOGICAL Default:

.FALSE.

If .TRUE. a saw-like potential simulating an electric field is added to the bare ionic potential. See variables "edir", "eamp", "emaxpos", "eopreg" for the form and size of the added potential.

[Back to Top] dipfield

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LOGICAL



Default:

.FALSE.

If .TRUE. and tefield=.TRUE. a dipole correction is also added to the bare ionic potential - implements the recipe of L. Bengtsson, PRB 59, 12301 (1999). See variables "edir", "emaxpos", "eopreg" for the form of the correction. Must be used ONLY in a slab geometry, for surface calculations, with the discontinuity FALLING IN THE EMPTY SPACE.

[Back to Top] lelfield

LOGICAL Default:

.FALSE.

If .TRUE. a homogeneous finite electric field described through the modern theory of the polarization is applied. This is different from "tefield=.true." !

[Back to Top] nberrycyc Default:

INTEGER 1

In the case of a finite electric field ( lelfield == .TRUE. ) it defines the number of iterations for converging the wavefunctions in the electric field Hamiltonian, for each external iteration on the charge density

[Back to Top] lorbm

LOGICAL Default:

.FALSE.

If .TRUE. perform orbital magnetization calculation. If finite electric field is applied (lelfield=.true.) only Kubo terms are computed [for details see New J. Phys. 12, 053032 (2010)]. The type of calculation is 'nscf' and should be performed on an automatically generated uniform grid of k points. Works ONLY with norm-conserving pseudopotentials.

[Back to Top] lberry

LOGICAL Default:

.FALSE.

If .TRUE. perform a Berry phase calculation See the header of PW/src/bp_c_phase.f90 for documentation

[Back to Top] gdir

INTEGER For Berry phase calculation: direction of the k-point strings in reciprocal space. Allowed values: 1, 2, 3 1=first, 2=second, 3=third reciprocal lattice vector For calculations with finite electric fields (lelfield==.true.) "gdir" is the direction of the field

[Back to Top] nppstr

INTEGER

For Berry phase calculation: number of k-points to be calculated along each symmetry-reduced string The same for calculation with finite electric fields (lelfield=.true.)

[Back to Top] lfcpopt

LOGICAL Default:

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.FALSE.



See:

fcp_mu

If .TRUE. perform a constant bias potential (constant-mu) calculation for a static system with ESM method. See the header of PW/src/fcp.f90 for documentation NB: - The total energy displayed in 'prefix.out' includes the potentiostat contribution (-mu*N). - 'calculation' must be 'relax'. - assume_isolated = 'esm' and esm_bc = 'bc2' or 'bc3' must be set in SYSTEM namelist).

[Back to Top]

Namelist: SYSTEM ibrav

INTEGER Status:

REQUIRED

Bravais-lattice index. If ibrav /= 0, specify EITHER [ celldm(1)-celldm(6) ] OR [ A,B,C,cosAB,cosAC,cosBC ] but NOT both. The lattice parameter "alat" is set to alat = celldm(1) (in a.u.) or alat = A (in Angstrom); see below for the other parameters. For ibrav=0 specify the lattice vectors in CELL_PARAMETER, optionally the lattice parameter alat = celldm(1) (in a.u.) or = A (in Angstrom), or else it is taken from CELL_PARAMETERS ibrav 0

structure

celldm(2)-celldm(6) or: b,c,cosab,cosac,cosbc free crystal axis provided in input: see card CELL_PARAMETERS

1

cubic P (sc) v1 = a(1,0,0), v2 = a(0,1,0),

2

cubic F (fcc) v1 = (a/2)(-1,0,1), v2 = (a/2)(0,1,1), v3 = (a/2)(-1,1,0)

3

cubic I (bcc) v1 = (a/2)(1,1,1), v2 = (a/2)(-1,1,1),

4

Hexagonal and Trigonal P celldm(3)=c/a v1 = a(1,0,0), v2 = a(-1/2,sqrt(3)/2,0), v3 = a(0,0,c/a)

5

Trigonal R, 3fold axis c celldm(4)=cos(alpha) The crystallographic vectors form a three-fold star around the z-axis, the primitive cell is a simple rhombohedron: v1 = a(tx,-ty,tz), v2 = a(0,2ty,tz), v3 = a(-tx,-ty,tz) where c=cos(alpha) is the cosine of the angle alpha between any pair of crystallographic vectors, tx, ty, tz are: tx=sqrt((1-c)/2), ty=sqrt((1-c)/6), tz=sqrt((1+2c)/3) Trigonal R, 3fold axis celldm(4)=cos(alpha) The crystallographic vectors form a three-fold star around . Defining a' = a/sqrt(3) : v1 = a' (u,v,v), v2 = a' (v,u,v), v3 = a' (v,v,u) where u and v are defined as u = tz - 2*sqrt(2)*ty, v = tz + sqrt(2)*ty and tx, ty, tz as for case ibrav=5 Note: if you prefer x,y,z as axis in the cubic limit, set u = tz + 2*sqrt(2)*ty, v = tz - sqrt(2)*ty See also the note in flib/latgen.f90

-5

v3 = (a/2)(-1,-1,1)

6

Tetragonal P (st) v1 = a(1,0,0), v2 = a(0,1,0),

7

Tetragonal I (bct) celldm(3)=c/a v1=(a/2)(1,-1,c/a), v2=(a/2)(1,1,c/a), v3=(a/2)(-1,-1,c/a)

8

9

-9

10

celldm(3)=c/a v3 = a(0,0,c/a)

Orthorhombic P v1 = (a,0,0),

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v3 = a(0,0,1)

celldm(2)=b/a celldm(3)=c/a v2 = (0,b,0), v3 = (0,0,c)

Orthorhombic base-centered(bco) celldm(2)=b/a celldm(3)=c/a v3 = (0,0,c)

v1 = (a/2, b/2,0), v2 = (-a/2,b/2,0), as 9, alternate description v1 = (a/2,-b/2,0), v2 = (a/2,-b/2,0), Orthorhombic face-centered

v3 = (0,0,c) celldm(2)=b/a



v1 = (a/2,0,c/2), 11

v2 = (a/2,b/2,0),

Orthorhombic body-centered v1=(a/2,b/2,c/2),

12

v2=(-a/2,b/2,c/2),

celldm(3)=c/a v3 = (0,b/2,c/2) celldm(2)=b/a celldm(3)=c/a v3=(-a/2,-b/2,c/2)

Monoclinic P, unique axis c

celldm(2)=b/a celldm(3)=c/a, celldm(4)=cos(ab) v1=(a,0,0), v2=(b*cos(gamma),b*sin(gamma),0), v3 = (0,0,c) where gamma is the angle between axis a and b. Monoclinic P, unique axis b celldm(2)=b/a celldm(3)=c/a, celldm(5)=cos(ac) v1 = (a,0,0), v2 = (0,b,0), v3 = (c*cos(beta),0,c*sin(beta)) where beta is the angle between axis a and c

-12

13

Monoclinic base-centered

celldm(2)=b/a celldm(3)=c/a, celldm(4)=cos(ab) -c/2),

v1 = ( a/2, 0, v2 = (b*cos(gamma), b*sin(gamma), 0), v3 = ( a/2, 0, c/2), where gamma is the angle between axis a and b 14

Triclinic

celldm(2)= celldm(3)= celldm(4)= celldm(5)= celldm(6)=

b/a, c/a, cos(bc), cos(ac), cos(ab)

v1 = (a, 0, 0), v2 = (b*cos(gamma), b*sin(gamma), 0) v3 = (c*cos(beta), c*(cos(alpha)-cos(beta)cos(gamma))/sin(gamma), c*sqrt( 1 + 2*cos(alpha)cos(beta)cos(gamma) - cos(alpha)^2-cos(beta)^2-cos(gamma)^2 )/sin(gamma) ) where alpha is the angle between axis b and c beta is the angle between axis a and c gamma is the angle between axis a and b

[Back to Top] Either: celldm(i), i=1,6 See:

REAL ibrav

Crystallographic constants - see the "ibrav" variable. Specify either these OR A,B,C,cosAB,cosBC,cosAC NOT both. Only needed values (depending on "ibrav") must be specified alat = celldm(1) is the lattice parameter "a" (in BOHR) If ibrav=0, only celldm(1) is used if present; cell vectors are read from card CELL_PARAMETERS

[Back to Top] Or: A, B, C, cosAB, cosAC, cosBC REAL Traditional crystallographic constants: a,b,c in ANGSTROM cosAB = cosine of the angle between axis a and b (gamma) cosAC = cosine of the angle between axis a and c (beta) cosBC = cosine of the angle between axis b and c (alpha) The axis are chosen according to the value of "ibrav". Specify either these OR "celldm" but NOT both. Only needed values (depending on "ibrav") must be specified The lattice parameter alat = A (in ANGSTROM ) If ibrav = 0, only A is used if present; cell vectors are read from card CELL_PARAMETERS

[Back to Top] nat

INTEGER Status:

REQUIRED

number of atoms in the unit cell

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[Back to Top] ntyp

INTEGER Status:

REQUIRED

number of types of atoms in the unit cell

[Back to Top] nbnd

INTEGER Default:

for an insulator, nbnd = number of valence bands (nbnd = # of electrons /2); for a metal, 20% more (minimum 4 more)

number of electronic states (bands) to be calculated. Note that in spin-polarized calculations the number of k-point, not the number of bands per k-point, is doubled

[Back to Top] tot_charge Default:

REAL 0.0

total charge of the By default the unit tot_charge=+1 means tot_charge=-1 means

system. Useful for simulations with charged cells. cell is assumed to be neutral (tot_charge=0). one electron missing from the system, one additional electron, and so on.

In a periodic calculation a compensating jellium background is inserted to remove divergences if the cell is not neutral.

[Back to Top] tot_magnetization REAL Default:

-1 [unspecified]

total majority spin charge - minority spin charge. Used to impose a specific total electronic magnetization. If unspecified then tot_magnetization variable is ignored and the amount of electronic magnetization is determined during the self-consistent cycle.

[Back to Top] starting_magnetization(i), i=1,ntyp REAL starting spin polarization on atomic type 'i' in a spin polarized calculation. Values range between -1 (all spins down for the valence electrons of atom type 'i') to 1 (all spins up). Breaks the symmetry and provides a starting point for self-consistency. The default value is zero, BUT a value MUST be specified for AT LEAST one atomic type in spin polarized calculations, unless you constrain the magnetization (see "tot_magnetization" and "constrained_magnetization"). Note that if you start from zero initial magnetization, you will invariably end up in a nonmagnetic (zero magnetization) state. If you want to start from an antiferromagnetic state, you may need to define two different atomic species corresponding to sublattices of the same atomic type. starting_magnetization is ignored if you are performing a non-scf calculation, if you are restarting from a previous run, or restarting from an interrupted run. If you fix the magnetization with "tot_magnetization", you should not specify starting_magnetization. In the spin-orbit case starting with zero starting_magnetization on all atoms imposes time reversal symmetry. The magnetization is never calculated and kept zero (the internal variable domag is .FALSE.).

[Back to Top] ecutwfc

REAL Status:

REQUIRED

kinetic energy cutoff (Ry) for wavefunctions

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[Back to Top] ecutrho

REAL Default:

4 * ecutwfc

kinetic energy cutoff (Ry) for charge density and potential For norm-conserving pseudopotential you should stick to the default value, you can reduce it by a little but it will introduce noise especially on forces and stress. If there are ultrasoft PP, a larger value than the default is often desirable (ecutrho = 8 to 12 times ecutwfc, typically). PAW datasets can often be used at 4*ecutwfc, but it depends on the shape of augmentation charge: testing is mandatory. The use of gradient-corrected functional, especially in cells with vacuum, or for pseudopotential without non-linear core correction, usually requires an higher values of ecutrho to be accurately converged.

[Back to Top] ecutfock

REAL Default:

ecutrho

kinetic energy cutoff (Ry) for the exact exchange operator in EXX type calculations. By default this is the same as ecutrho but in some EXX calculations significant speed-up can be found by reducing ecutfock, at the expense of some loss in accuracy. Must be .gt. ecutwfc. Not implemented for stress calculation. Use with care, especially in metals where it may give raise to instabilities.

[Back to Top] nr1, nr2, nr3

INTEGER

three-dimensional FFT mesh (hard grid) for charge density (and scf potential). If not specified the grid is calculated based on the cutoff for charge density (see also "ecutrho") Note: you must specify all three dimensions for this setting to be used.

[Back to Top] nr1s, nr2s, nr3s

INTEGER

three-dimensional mesh for wavefunction FFT and for the smooth part of charge density ( smooth grid ). Coincides with nr1, nr2, nr3 if ecutrho = 4 * ecutwfc ( default ) Note: you must specify all three dimensions for this setting to be used.

[Back to Top] nosym

LOGICAL Default:

.FALSE.

if (.TRUE.) symmetry is not used. Note that - if the k-point grid is provided in input, it is used "as is" and symmetry-inequivalent k-points are not generated; - if the k-point grid is automatically generated, it will contain only points in the irreducible BZ for the bravais lattice, irrespective of the actual crystal symmetry. A careful usage of this option can be advantageous - in low-symmetry large cells, if you cannot afford a k-point grid with the correct symmetry - in MD simulations - in calculations for isolated atoms

[Back to Top] nosym_evc Default:

LOGICAL .FALSE.

if(.TRUE.) symmetry is not used but the k-points are forced to have the symmetry of the Bravais lattice; an automatically generated k-point grid will contain

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all the k-points of the grid and the points rotated by the symmetries of the Bravais lattice which are not in the original grid. If available, time reversal is used to reduce the k-points (and the q => -q symmetry is used in the phonon code). To disable also this symmetry set noinv=.TRUE..

[Back to Top] noinv

LOGICAL Default:

.FALSE.

if (.TRUE.) disable the usage of k => -k symmetry (time reversal) in k-point generation

[Back to Top] no_t_rev

LOGICAL Default:

.FALSE.

if (.TRUE.) disable the usage of magnetic symmetry operations that consist in a rotation + time reversal.

[Back to Top] force_symmorphic LOGICAL Default:

.FALSE.

if (.TRUE.) force the symmetry group to be symmorphic by disabling symmetry operations having an associated fractionary translation

[Back to Top] use_all_frac

LOGICAL

Default:

.FALSE.

if (.TRUE.) do not discard symmetry operations with an associated fractionary translation that does not send the real-space FFT grid into itself. These operations are incompatible with real-space symmetrization but not with the new G-space symmetrization. BEWARE: do not use for phonons! The phonon code still uses real-space symmetrization.

[Back to Top] occupations

CHARACTER

'smearing':

gaussian smearing for metals see variables 'smearing' and 'degauss'

'tetrahedra' :

especially suited for calculation of DOS (see P.E. Bloechl, PRB49, 16223 (1994)) Requires uniform grid of k-points, automatically generated (see below) Not suitable (because not variational) for force/optimization/dynamics calculations

'fixed' :

for insulators with a gap

'from_input' :

The occupation are read from input file, card OCCUPATIONS. Option valid only for a single k-point, requires "nbnd" to be set in input. Occupations should be consistent with the value of "tot_charge".

[Back to Top] one_atom_occupations LOGICAL Default:

.FALSE.

This flag is used for isolated atoms (nat=1) together with occupations='from_input'. If it is .TRUE., the wavefunctions are ordered as the atomic starting wavefunctions, independently from their eigenvalue. The occupations indicate which atomic

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states are filled. The order of the states is written inside the UPF pseudopotential file. In the scalar relativistic case: S -> l=0, m=0 P -> l=1, z, x, y D -> l=2, r^2-3z^2, xz, yz, xy, x^2-y^2 In the noncollinear magnetic case (with or without spin-orbit), each group of states is doubled. For instance: P -> l=1, z, x, y for spin up, l=1, z, x, y for spin down. Up and down is relative to the direction of the starting magnetization. In the case with spin-orbit and time-reversal (starting_magnetization=0.0) the atomic wavefunctions are radial functions multiplied by spin-angle functions. For instance: P -> l=1, j=1/2, m_j=-1/2,1/2. l=1, j=3/2, m_j=-3/2, -1/2, 1/2, 3/2. In the magnetic case with spin-orbit the atomic wavefunctions can be forced to be spin-angle functions by setting starting_spin_angle to .TRUE..

[Back to Top] starting_spin_angle LOGICAL Default:

.FALSE.

In the spin-orbit case when domag=.TRUE., by default, the starting wavefunctions are initialized as in scalar relativistic noncollinear case without spin-orbit. By setting starting_spin_angle=.TRUE. this behaviour can be changed and the initial wavefunctions are radial functions multiplied by spin-angle functions. When domag=.FALSE. the initial wavefunctions are always radial functions multiplied by spin-angle functions independently from this flag. When lspinorb is .FALSE. this flag is not used.

[Back to Top] degauss

REAL Default:

0.D0 Ry

value of the gaussian spreading (Ry) for brillouin-zone integration in metals.

[Back to Top] smearing

CHARACTER Default:

'gaussian'

'gaussian', 'gauss': ordinary Gaussian spreading (Default) 'methfessel-paxton', 'm-p', 'mp': Methfessel-Paxton first-order spreading (see PRB 40, 3616 (1989)). 'marzari-vanderbilt', 'cold', 'm-v', 'mv': Marzari-Vanderbilt cold smearing (see PRL 82, 3296 (1999)) 'fermi-dirac', 'f-d', 'fd': smearing with Fermi-Dirac function

[Back to Top] nspin

INTEGER Default:

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1

nspin = 1 :

non-polarized calculation (default)

nspin = 2 :

spin-polarized calculation, LSDA (magnetization along z axis)

nspin = 4 :

spin-polarized calculation, noncollinear (magnetization in generic direction) DO NOT specify nspin in this case;



specify "noncolin=.TRUE." instead

[Back to Top] noncolin

LOGICAL Default:

.false.

if .true. the program will perform a noncollinear calculation.

[Back to Top] ecfixed

REAL Default: See:

0.0 q2sigma [Back to Top]

qcutz

REAL Default: See:

0.0 q2sigma [Back to Top]

q2sigma

REAL Default:

0.1

ecfixed, qcutz, q2sigma: parameters for modified functional to be used in variable-cell molecular dynamics (or in stress calculation). "ecfixed" is the value (in Rydberg) of the constant-cutoff; "qcutz" and "q2sigma" are the height and the width (in Rydberg) of the energy step for reciprocal vectors whose square modulus is greater than "ecfixed". In the kinetic energy, G^2 is replaced by G^2 + qcutz * (1 + erf ( (G^2 - ecfixed)/q2sigma) ) See: M. Bernasconi et al, J. Phys. Chem. Solids 56, 501 (1995)

[Back to Top] input_dft

CHARACTER Default:

read from pseudopotential files

Exchange-correlation functional: eg 'PBE', 'BLYP' etc See Modules/functionals.f90 for allowed values. Overrides the value read from pseudopotential files. Use with care and if you know what you are doing!

[Back to Top] exx_fraction

REAL

Default:

it depends on the specified functional

Fraction of EXX for hybrid functional calculations. In the case of input_dft='PBE0', the default value is 0.25, while for input_dft='B3LYP' the exx_fraction default value is 0.20.

[Back to Top] screening_parameter REAL Default:

0.106

screening_parameter for HSE like hybrid functionals. See J. Chem. Phys. 118, 8207 (2003) and J. Chem. Phys. 124, 219906 (2006) for more informations.

[Back to Top] exxdiv_treatment CHARACTER Default:

gygi-baldereschi

Specific for EXX. It selects the kind of approach to be used for treating the Coulomb potential divergencies at small q vectors. gygi-baldereschi : appropriate for cubic and quasi-cubic supercells

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vcut_spherical : appropriate for cubic and quasi-cubic supercells vcut_ws : appropriate for strongly anisotropic supercells, see also ecutvcut. none : sets Coulomb potential at G,q=0 to 0.0 (required for GAU-PBE)

[Back to Top] x_gamma_extrapolation LOGICAL Default:

.true.

Specific for EXX. If true, extrapolate the G=0 term of the potential (see README in examples/EXX_example for more) Set this to .false. for GAU-PBE.

[Back to Top] ecutvcut

REAL Default: See:

0.0 Ry exxdiv_treatment

Reciprocal space cutoff for correcting Coulomb potential divergencies at small q vectors.

[Back to Top] nqx1, nqx2, nqx3 INTEGER three-dimensional mesh for q (k1-k2) sampling of the Fock operator (EXX). Can be smaller than the number of k-points. Currently this defaults to the size of the k-point mesh used. In QE =< 5.0.2 it defaulted to nqx1=nqx2=nqx3=1.

[Back to Top] lda_plus_u

LOGICAL

Default: Status:

.FALSE. DFT+U (formerly known as LDA+U) currently works only for a few selected elements. Modify flib/set_hubbard_l.f90 and PW/src/tabd.f90 if you plan to use DFT+U with an element that is not configured there.

Specify lda_plus_u = .TRUE. to enable DFT+U calculations See: Anisimov, Zaanen, and Andersen, PRB 44, 943 (1991); Anisimov et al., PRB 48, 16929 (1993); Liechtenstein, Anisimov, and Zaanen, PRB 52, R5467 (1994). You must specify, for each species with a U term, the value of U and (optionally) alpha, J of the Hubbard model (all in eV): see lda_plus_u_kind, Hubbard_U, Hubbard_alpha, Hubbard_J

[Back to Top] lda_plus_u_kind Default:

INTEGER 0

Specifies the type of DFT+U calculation: 0 simplified version of Cococcioni and de Gironcoli, PRB 71, 035105 (2005), using Hubbard_U 1 rotationally invariant scheme of Liechtenstein et al., using Hubbard_U and Hubbard_J

[Back to Top] Hubbard_U(i), i=1,ntyp REAL Default:

0.D0 for all species

Hubbard_U(i): U parameter (eV) for species i, DFT+U calculation

[Back to Top] Hubbard_J0(i), i=1,ntype REAL

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Default:


Hubbard_J0(i): J0 parameter (eV) for species i, DFT+U+J calculation, see PRB 84, 115108 (2011) for details.

[Back to Top] Hubbard_alpha(i), i=1,ntyp REAL Default:


Hubbard_alpha(i) is the perturbation (on atom i, in eV) used to compute U with the linear-response method of Cococcioni and de Gironcoli, PRB 71, 35105 (2005) (only for lda_plus_u_kind=0)

[Back to Top] Hubbard_beta(i), i=1,ntyp REAL Default:


Hubbard_beta(i) is the perturbation (on atom i, in eV) used to compute J0 with the linear-response method of Cococcioni and de Gironcoli, PRB 71, 35105 (2005) (only for lda_plus_u_kind=0). See also PRB 84, 115108 (2011).

[Back to Top] Hubbard_J(i,ityp) Default:


Hubbard_J(i,ityp): J parameters (eV) for species ityp, used in DFT+U calculations (only for lda_plus_u_kind=1) For p orbitals: J = Hubbard_J(1,ityp); For d orbitals: J = Hubbard_J(1,ityp), B = Hubbard_J(2,ityp); For f orbitals: J = Hubbard_J(1,ityp), E2 = Hubbard_J(2,ityp), E3= Hubbard_J(3,ityp). If B or E2 or E3 are not specified or set to 0 they will be calculated from J using atomic ratios.

[Back to Top] starting_ns_eigenvalue(m,ispin,I) REAL Default:

-1.d0 that means NOT SET

In the first iteration of an DFT+U run it overwrites the m-th eigenvalue of the ns occupation matrix for the ispin component of atomic species I. Leave unchanged eigenvalues that are not set. This is useful to suggest the desired orbital occupations when the default choice takes another path.

[Back to Top] U_projection_type CHARACTER Default:

'atomic'

Only active when lda_plus_U is .true., specifies the type of projector on localized orbital to be used in the DFT+U scheme. Currently available choices: 'atomic': use atomic wfc's (as they are) to build the projector 'ortho-atomic': use Lowdin orthogonalized atomic wfc's

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'norm-atomic':

Lowdin normalization of atomic wfc. Keep in mind: atomic wfc are not orthogonalized in this case. This is a "quick and dirty" trick to be used when atomic wfc from the pseudopotential are not normalized (and thus produce occupation whose value exceeds unity). If orthogonalized wfc are not needed always try 'atomic' first.

'file':

use the information from file "prefix".atwfc that must



have been generated previously, for instance by pmw.x (see PP/src/poormanwannier.f90 for details). 'pseudo':

use the pseudopotential projectors. The charge density outside the atomic core radii is excluded. N.B.: for atoms with +U, a pseudopotential with the all-electron atomic wavefunctions is required (i.e., as generated by ld1.x with lsave_wfc flag).

NB: forces and stress currently implemented only for the 'atomic' and 'pseudo' choice.

[Back to Top] edir

INTEGER The direction of the electric field or dipole correction is parallel to the bg(:,edir) reciprocal lattice vector, so the potential is constant in planes defined by FFT grid points; edir = 1, 2 or 3. Used only if tefield is .TRUE.

[Back to Top] emaxpos

REAL Default:

0.5D0

Position of the maximum of the saw-like potential along crystal axis "edir", within the unit cell (see below), 0 < emaxpos < 1 Used only if tefield is .TRUE.

[Back to Top] eopreg

REAL Default:

0.1D0

Zone in the unit cell where the saw-like potential decreases. ( see below, 0 < eopreg < 1 ). Used only if tefield is .TRUE.

[Back to Top] eamp

REAL Default:

0.001 a.u.

Amplitude of the electric field, in ***Hartree*** a.u.; 1 a.u. = 51.4220632*10^10 V/m). Used only if tefield=.TRUE. The saw-like potential increases with slope "eamp" in the region from (emaxpos+eopreg-1) to (emaxpos), then decreases to 0 until (emaxpos+eopreg), in units of the crystal vector "edir". Important: the change of slope of this potential must be located in the empty region, or else unphysical forces will result.

[Back to Top] angle1(i), i=1,ntyp REAL The angle expressed in degrees between the initial magnetization and the z-axis. For noncollinear calculations only; index i runs over the atom types.

[Back to Top] angle2(i), i=1,ntyp REAL The angle expressed in degrees between the projection of the initial magnetization on x-y plane and the x-axis. For noncollinear calculations only.

[Back to Top] constrained_magnetization CHARACTER Default:

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'none'



See:

lambda, fixed_magnetization

Used to perform constrained calculations in magnetic systems. Currently available choices: 'none': no constraint 'total': total magnetization is constrained by adding a penalty functional to the total energy: LAMBDA * SUM_{i} ( magnetization(i) - fixed_magnetization(i) )**2 where the sum over i runs over the three components of the magnetization. Lambda is a real number (see below). Noncolinear case only. Use "tot_magnetization" for LSDA 'atomic': atomic magnetization are constrained to the defined starting magnetization adding a penalty: LAMBDA * SUM_{i,itype} ( magnetic_moment(i,itype) - mcons(i,itype) )**2 where i runs over the cartesian components (or just z in the collinear case) and itype over the types (1-ntype). mcons(:,:) array is defined from starting_magnetization, (and angle1, angle2 in the non-collinear case). lambda is a real number 'total direction': the angle theta of the total magnetization with the z axis (theta = fixed_magnetization(3)) is constrained: LAMBDA * ( arccos(magnetization(3)/mag_tot) - theta )**2 where mag_tot is the modulus of the total magnetization. 'atomic direction': not all the components of the atomic magnetic moment are constrained but only the cosine of angle1, and the penalty functional is: LAMBDA * SUM_{itype} ( mag_mom(3,itype)/mag_mom_tot - cos(angle1(ityp)) )**2 N.B.: symmetrization may prevent to reach the desired orientation of the magnetization. Try not to start with very highly symmetric configurations or use the nosym flag (only as a last remedy)

[Back to Top] fixed_magnetization(i), i=1,3 REAL Default: See:

0.d0 constrained_magnetization

total magnetization vector (x,y,z components) to be kept fixed when constrained_magnetization='total'

[Back to Top] lambda

REAL Default: See:

1.d0 constrained_magnetization

parameter used for constrained_magnetization calculations N.B.: if the scf calculation does not converge, try to reduce lambda to obtain convergence, then restart the run with a larger lambda

[Back to Top] report

INTEGER Default:

1

It is the number of iterations after which the program write all the atomic magnetic moments.

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[Back to Top] lspinorb

LOGICAL

if .TRUE. the noncollinear code can use a pseudopotential with spin-orbit.

[Back to Top] assume_isolated CHARACTER Default:

'none'

Used to perform calculation assuming the system to be isolated (a molecule or a cluster in a 3D supercell). Currently available choices: 'none' (default): regular periodic calculation w/o any correction. 'makov-payne', 'm-p', 'mp' : the Makov-Payne correction to the total energy is computed. An estimate of the vacuum level is also calculated so that eigenvalues can be properly aligned. ONLY FOR CUBIC SYSTEMS (ibrav=1,2,3) Theory: G.Makov, and M.C.Payne, "Periodic boundary conditions in ab initio calculations" , Phys.Rev.B 51, 4014 (1995) 'martyna-tuckerman', 'm-t', 'mt' : Martyna-Tuckerman correction to both total energy and scf potential. Adapted from: G.J. Martyna, and M.E. Tuckerman, "A reciprocal space based method for treating long range interactions in ab-initio and force-field-based calculation in clusters", J.Chem.Phys. 110, 2810 (1999) 'esm' :

Effective Screening Medium Method. For polarized or charged slab calculation, embeds the simulation cell within an effective semiinfinite medium in the perpendicular direction (along z). Embedding regions can be vacuum or semi-infinite metal electrodes (use 'esm_bc' to choose boundary conditions). If between two electrodes, an optional electric field ('esm_efield') may be applied. Method described in M. Otani and O. Sugino, "First-principles calculations of charged surfaces and interfaces: A plane-wave nonrepeated slab approach," PRB 73, 115407 (2006). NB: - Two dimensional (xy plane) average charge density and electrostatic potentials are printed out to 'prefix.esm1'. - Requires cell with a_3 lattice vector along z, normal to the xy plane, with the slab centered around z=0. Also requires symmetry checking to be disabled along z, either by setting 'nosym' = .TRUE. or by very slight displacement (i.e., 5e-4 a.u.) of the slab along z. See 'esm_bc', 'esm_efield', 'esm_w', 'esm_nfit'.

[Back to Top] esm_bc

CHARACTER Default: See:

'pbc' assume_isolated

If assume_isolated = 'esm', determines the boundary conditions used for either side of the slab. Currently available choices: 'pbc' (default): regular periodic calculation (no ESM). 'bc1' : Vacuum-slab-vacuum (open boundary conditions) 'bc2' : Metal-slab-metal (dual electrode configuration). See also 'esm_efield'. 'bc3' : Vacuum-slab-metal

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[Back to Top] esm_w

REAL Default: See:

0.d0 assume_isolated

If assume_isolated = 'esm', determines the position offset [in a.u.] of the start of the effective screening region, measured relative to the cell edge. (ESM region begins at z = +/- [L_z/2 + esm_w] ).

[Back to Top] esm_efield

REAL

Default: See:

0.d0 assume_isolated

If assume_isolated = 'esm' and esm_bc = 'bc2', gives the magnitude of the electric field [Ry/a.u.] to be applied between semi-infinite ESM electrodes.

[Back to Top] esm_nfit

INTEGER Default: See:

4 assume_isolated

If assume_isolated = 'esm', gives the number of z-grid points for the polynomial fit along the cell edge.

[Back to Top] fcp_mu

REAL Default: See:

0.d0 lfcpopt

If lfcpopt = .TRUE., gives the target Fermi energy [Ry]. One can start with appropriate total charge of the system by giving 'tot_charge'.

[Back to Top] vdw_corr

CHARACTER Default:

'none'

Type of Van der Waals correction. Allowed values: 'grimme-d2', 'Grimme-D2', 'DFT-D', 'dft-d': semiempirical Grimme's DFT-D2. Optional variables: "london_s6", "london_rcut", "london_c6" S. Grimme, J. Comp. Chem. 27, 1787 (2006), V. Barone et al., J. Comp. Chem. 30, 934 (2009). 'TS', 'ts', 'ts-vdw', 'ts-vdW', 'tkatchenko-scheffler': Tkatchenko-Scheffler dispersion corrections with first-principle derived C6 coefficients (implemented in CP only). Optional variables: "ts_vdw_econv_thr", "ts_vdw_isolated" See A. Tkatchenko and M. Scheffler, Phys. Rev. Lett. 102, 073005 (2009) 'XDM', 'xdm': Exchange-hole dipole-moment model. Optional variables: "xdm_a1", "xdm_a2" A. D. Becke and E. R. Johnson, J. Chem. Phys. 127, 154108 (2007) A. Otero de la Roza, E. R. Johnson, J. Chem. Phys. 136, 174109 (2012) Note that non-local functionals (eg vdw-DF) are NOT specified here but in "input_dft"

[Back to Top] london

LOGICAL Default:

.FALSE.

OBSOLESCENT, same as vdw_corr='DFT-D'

[Back to Top] london_s6

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REAL



Default:

0.75

global scaling parameter for DFT-D. Default is good for PBE.

[Back to Top] london_c6(i), i=1,ntyp REAL Default:

standard Grimme-D2 values

atomic C6 coefficient of each atom type ( if not specified default values from S. Grimme, J. Comp. Chem. 27, 1787 (2006) are used; see file Modules/mm_dispersion.f90 )

[Back to Top] london_rcut Default:

REAL 200

cutoff radius (a.u.) for dispersion interactions

[Back to Top] xdm

LOGICAL Default:

.FALSE.

OBSOLESCENT, same as vdw_corr='xdm'

[Back to Top] xdm_a1

REAL Default:

0.6836

Damping function parameter a1 (adimensional). This value should change with the exchange-correlation functional. The default corresponds to PW86PBE. For other functionals, see: http://gatsby.ucmerced.edu/wiki/XDM_damping_function_parameters A. Otero de la Roza, E. R. Johnson, J. Chem. Phys. 138, 204109 (2013)

[Back to Top] xdm_a2

REAL Default:

1.5045

Damping function parameter a2 (angstrom). This value should change with the exchange-correlation functional. The default corresponds to PW86PBE. For other functionals, see: http://gatsby.ucmerced.edu/wiki/XDM_damping_function_parameters A. Otero de la Roza, E. R. Johnson, J. Chem. Phys. 138, 204109 (2013)

[Back to Top] space_group Default:

INTEGER 0

The number of the space group of the crystal, as given in the International Tables of Crystallography A (ITA). This allows to give in input only the inequivalent atomic positions. The positions of all the symmetry equivalent atoms are calculated by the code. Used only when the atomic positions are of type crystal_sg.

[Back to Top] uniqueb

LOGICAL Default:

.FALSE.

Used only for monoclinic lattices. If .TRUE. the b unique ibrav (-12 or -13) are used, and symmetry

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equivalent positions are chosen assuming that the two fold axis or the mirror normal is parallel to the b axis. If .FALSE. it is parallel to the c axis.

[Back to Top] origin_choice

INTEGER

Default:

1

Used only for space groups that in the ITA allow the use of two different origins. origin_choice=1, means the first origin, while origin_choice=2 is the second origin.

[Back to Top] rhombohedral

LOGICAL

Default:

.TRUE.

Used only for rhombohedral space groups. When .TRUE. the coordinates of the inequivalent atoms are given with respect to the rhombohedral axes, when .FALSE. the coordinates of the inequivalent atoms are given with respect to the hexagonal axes. They are converted internally to the rhombohedral axes and ibrav=5 is used in both cases.

[Back to Top]

Namelist: ELECTRONS electron_maxstep INTEGER Default:

100

maximum number of iterations in a scf step

[Back to Top] scf_must_converge LOGICAL Default:

.TRUE.

If .false. do not stop molecular dynamics or ionic relaxation when electron_maxstep is reached. Use with care.

[Back to Top] conv_thr Default:

REAL 1.D-6

Convergence threshold for selfconsistency: estimated energy error < conv_thr (note that conv_thr is extensive, like the total energy). For non-self-consistent calculations, conv_thr is used to set the default value of the threshold (ethr) for iterative diagonalizazion: see diago_thr_init

[Back to Top] adaptive_thr Default:

LOGICAL .FALSE

If .TRUE. this turns on the use of an adaptive conv_thr for the inner scf loops when using EXX.

[Back to Top] conv_thr_init Default:

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REAL 1.D-3



When adaptive_thr = .TRUE. this is the convergence threshold used for the first scf cycle.

[Back to Top] conv_thr_multi

REAL

Default:

1.D-1

When adaptive_thr = .TRUE. the convergence threshold for each scf cycle is given by: max( conv_thr, conv_thr_multi * dexx )

[Back to Top] mixing_mode

CHARACTER

Default: 'plain' :

'plain' charge density Broyden mixing

'TF' :

as above, with simple Thomas-Fermi screening (for highly homogeneous systems)

'local-TF':

as above, with local-density-dependent TF screening (for highly inhomogeneous systems)

[Back to Top] mixing_beta

REAL

Default:

0.7D0

mixing factor for self-consistency

[Back to Top] mixing_ndim

INTEGER

Default:

8

number of iterations used in mixing scheme. If you are tight with memory, you may reduce it to 4 or so.

[Back to Top] mixing_fixed_ns INTEGER Default:

0

For DFT+U : number of iterations with fixed ns ( ns is the atomic density appearing in the Hubbard term ).

[Back to Top] diagonalization Default:

CHARACTER 'david'

'david':

Davidson iterative diagonalization with overlap matrix (default). Fast, may in some rare cases fail.

'cg' :

conjugate-gradient-like band-by-band diagonalization Typically slower than 'david' but it uses less memory and is more robust (it seldom fails)

'cg-serial', 'david-serial': obsolete, use "-ndiag 1 instead" The subspace diagonalization in Davidson is performed by a fully distributed-memory parallel algorithm on 4 or more processors, by default. The allocated memory scales down with the number of procs. Procs involved in diagonalization can be changed with command-line option "-ndiag N". On multicore CPUs it is often convenient to let just one core per CPU to work on linear algebra.

[Back to Top]

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ortho_para Default: Status:

INTEGER 0 OBSOLETE: use command-line option " -ndiag XX" instead

[Back to Top] diago_thr_init

REAL

Convergence threshold (ethr) for iterative diagonalization (the check is on eigenvalue convergence). For scf calculations: default is 1.D-2 if starting from a superposition of atomic orbitals; 1.D-5 if starting from a charge density. During self consistency the threshold is automatically reduced (but never below 1.D-13) when approaching convergence. For non-scf calculations: default is (conv_thr/N elec)/10.

[Back to Top] diago_cg_maxiter INTEGER For conjugate gradient diagonalization: max number of iterations

[Back to Top] diago_david_ndim INTEGER Default:

4

For Davidson diagonalization: dimension of workspace (number of wavefunction packets, at least 2 needed). A larger value may yield a somewhat faster algorithm but uses more memory. The opposite holds for smaller values. Try diago_david_ndim=2 if you are tight on memory or if your job is large: the speed penalty is often negligible

[Back to Top] diago_full_acc Default:

LOGICAL .FALSE.

If .TRUE. all the empty states are diagonalized at the same level of accuracy of the occupied ones. Otherwise the empty states are diagonalized using a larger threshold (this should not affect total energy, forces, and other ground-state properties).

[Back to Top] efield

REAL Default:

0.D0

Amplitude of the finite electric field (in Ry a.u.; 1 a.u. = 36.3609*10^10 V/m). Used only if lelfield=.TRUE. and if k-points (K_POINTS card) are not automatic.

[Back to Top] efield_cart(i), i=1,3 REAL Default:

(0.D0, 0.D0, 0.D0)

Finite electric field (in Ry a.u.=36.3609*10^10 V/m) in cartesian axis. Used only if lelfield=.TRUE. and if k-points (K_POINTS card) are automatic.

[Back to Top] startingpot

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CHARACTER



'atomic': starting potential from atomic charge superposition ( default for scf, *relax, *md ) 'file'

: start from existing "charge-density.xml" file in the directory specified by variables "prefix" and "outdir" For nscf and bands calculation this is the default and the only sensible possibility.

[Back to Top] startingwfc

CHARACTER

Default:

'atomic+random'

'atomic': start from superposition of atomic orbitals If not enough atomic orbitals are available, fill with random numbers the remaining wfcs The scf typically starts better with this option, but in some high-symmetry cases one can "loose" valence states, ending up in the wrong ground state. 'atomic+random': as above, plus a superimposed "randomization" of atomic orbitals. Prevents the "loss" of states mentioned above. 'random': start from random wfcs. Slower start of scf but safe. It may also reduce memory usage in conjunction with diagonalization='cg' 'file':

start from an existing wavefunction file in the directory specified by variables "prefix" and "outdir"

[Back to Top] tqr

LOGICAL Default:

.FALSE.

If .true., use the real-space algorithm for augmentation charges in ultrasoft pseudopotentials. Must faster execution of ultrasoft-related calculations, but numerically less accurate than the default algorithm. Use with care and after testing!

[Back to Top]

Namelist: IONS input this namelist only if calculation = 'relax', 'md', 'vc-relax', 'vc-md' ion_dynamics

CHARACTER

Specify the type of ionic dynamics. For different type of calculation different possibilities are allowed and different default values apply: CASE ( calculation = 'relax' ) 'bfgs' : (default) use BFGS quasi-newton algorithm, based on the trust radius procedure, for structural relaxation 'damp' : use damped (quick-min Verlet) dynamics for structural relaxation Can be used for constrained optimisation: see CONSTRAINTS card CASE ( calculation = 'md' ) 'verlet' : (default) use Verlet algorithm to integrate Newton's equation. For constrained dynamics, see CONSTRAINTS card 'langevin' ion dynamics is over-damped Langevin 'langevin-smc' over-damped Langevin with Smart Monte Carlo: see R.J.Rossky, JCP, 69, 4628(1978)

CASE ( calculation = 'vc-relax' ) 'bfgs' : (default) use BFGS quasi-newton algorithm;

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cell_dynamics must be 'bfgs' too use damped (Beeman) dynamics for structural relaxation CASE ( calculation = 'vc-md' ) 'beeman' : (default) use Beeman algorithm to integrate Newton's equation 'damp' :

[Back to Top] ion_positions

CHARACTER

Default: 'default '

'default' : if restarting, use atomic positions read from the restart file; in all other cases, use atomic positions from standard input.

'from_input' : restart the simulation with atomic positions read from standard input, even if restarting.

[Back to Top] pot_extrapolation CHARACTER Default:

'atomic'

Used to extrapolate the potential from preceding ionic steps. 'none'

:

no extrapolation

'atomic'

:

extrapolate the potential as if it was a sum of atomic-like orbitals

'first_order' :

extrapolate the potential with first-order formula

'second_order':

as above, with second order formula

Note: 'first_order' and 'second-order' extrapolation make sense only for molecular dynamics calculations

[Back to Top] wfc_extrapolation CHARACTER Default:

'none'

Used to extrapolate the wavefunctions from preceding ionic steps. 'none'

:

no extrapolation

'first_order' :

extrapolate the wave-functions with first-order formula.

'second_order':

as above, with second order formula.

Note: 'first_order' and 'second-order' extrapolation make sense only for molecular dynamics calculations

[Back to Top] remove_rigid_rot LOGICAL Default:

.FALSE.

This keyword is useful when simulating the dynamics and/or the thermodynamics of an isolated system. If set to true the total torque of the internal forces is set to zero by adding new forces that compensate the spurious interaction with the periodic images. This allows for the use of smaller supercells. BEWARE: since the potential energy is no longer consistent with the forces (it still contains the spurious interaction with the repeated images), the total energy is not conserved anymore. However the dynamical and thermodynamical properties should be in closer agreement with those of an isolated system. Also the final energy of a structural relaxation will be higher, but the relaxation itself should be faster.

[Back to Top]

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keywords used for molecular dynamics ion_temperature CHARACTER Default:

'not_controlled'

'rescaling'

control ionic temperature via velocity rescaling (first method) see parameters "tempw", "tolp", and "nraise" (for VC-MD only). This rescaling method is the only one currently implemented in VC-MD

'rescale-v'

control ionic temperature via velocity rescaling (second method) see parameters "tempw" and "nraise"

'rescale-T'

control ionic temperature via velocity rescaling (third method) see parameter "delta_t"

'reduce-T'

reduce ionic temperature every "nraise" steps by the (negative) value "delta_t"

'berendsen'

control ionic temperature using "soft" velocity rescaling - see parameters "tempw" and "nraise"

'andersen'

control ionic temperature using Andersen thermostat see parameters "tempw" and "nraise"

'initial'

initialize ion velocities to temperature "tempw" and leave uncontrolled further on

'not_controlled' (default) ionic temperature is not controlled

[Back to Top] tempw

REAL Default:

300.D0

Starting temperature (Kelvin) in MD runs target temperature for most thermostats.

[Back to Top] tolp

REAL Default:

100.D0

Tolerance for velocity rescaling. Velocities are rescaled if the run-averaged and target temperature differ more than tolp.

[Back to Top] delta_t

REAL Default:

1.D0

if ion_temperature='rescale-T': at each step the instantaneous temperature is multiplied by delta_t; this is done rescaling all the velocities. if ion_temperature='reduce-T': every 'nraise' steps the instantaneous temperature is reduced by -delta_T (i.e. delta_t < 0 is added to T) The instantaneous temperature is calculated at the end of every ionic move and BEFORE rescaling. This is the temperature reported in the main output. For delta_t < 0, the actual average rate of heating or cooling should be roughly C*delta_t/(nraise*dt) (C=1 for an ideal gas, C=0.5 for a harmonic solid, theorem of energy equipartition between all quadratic degrees of freedom).

[Back to Top] nraise

INTEGER Default:

1

if ion_temperature='reduce-T': every 'nraise' steps the instantaneous temperature is reduced by -delta_T (.e. delta_t is added to the temperature)

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if ion_temperature='rescale-v': every 'nraise' steps the average temperature, computed from the last nraise steps, is rescaled to tempw if ion_temperature='rescaling' and calculation='vc-md': every 'nraise' steps the instantaneous temperature is rescaled to tempw if ion_temperature='berendsen': the "rise time" parameter is given in units of the time step: tau = nraise*dt, so dt/tau = 1/nraise if ion_temperature='andersen': the "collision frequency" parameter is given as nu=1/tau defined above, so nu*dt = 1/nraise

[Back to Top] refold_pos Default:

LOGICAL .FALSE.

This keyword applies only in the case of molecular dynamics or damped dynamics. If true the ions are refolded at each step into the supercell.

[Back to Top] keywords used only in BFGS calculations upscale

REAL

Default:

100.D0

Max reduction factor for conv_thr during structural optimization conv_thr is automatically reduced when the relaxation approaches convergence so that forces are still accurate, but conv_thr will not be reduced to less that conv_thr / upscale.

[Back to Top] bfgs_ndim Default:

INTEGER 1

Number of old forces and displacements vectors used in the PULAY mixing of the residual vectors obtained on the basis of the inverse hessian matrix given by the BFGS algorithm. When bfgs_ndim = 1, the standard quasi-Newton BFGS method is used. (bfgs only)

[Back to Top] trust_radius_max REAL Default:

0.8D0

Maximum ionic displacement in the structural relaxation. (bfgs only)

[Back to Top] trust_radius_min REAL Default:

1.D-3

Minimum ionic displacement in the structural relaxation BFGS is reset when trust_radius < trust_radius_min. (bfgs only)

[Back to Top] trust_radius_ini REAL

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Default:

0.5D0

Initial ionic displacement in the structural relaxation. (bfgs only)

[Back to Top] w_1

REAL Default: See:

0.01D0 w_2 [Back to Top]

w_2

REAL Default:

0.5D0

Parameters used in line search based on the Wolfe conditions. (bfgs only)

[Back to Top]

Namelist: CELL input this namelist only if calculation = 'vc-relax', 'vc-md' cell_dynamics

CHARACTER

Specify the type of dynamics for the cell. For different type of calculation different possibilities are allowed and different default values apply: CASE ( calculation = 'vc-relax' ) 'none': no dynamics 'sd': steepest descent ( not implemented ) 'damp-pr': damped (Beeman) dynamics of the Parrinello-Rahman extended lagrangian 'damp-w': damped (Beeman) dynamics of the new Wentzcovitch extended lagrangian 'bfgs': BFGS quasi-newton algorithm (default) ion_dynamics must be 'bfgs' too CASE ( calculation = 'vc-md' ) 'none': no dynamics 'pr': (Beeman) molecular dynamics of the Parrinello-Rahman extended lagrangian 'w': (Beeman) molecular dynamics of the new Wentzcovitch extended lagrangian

[Back to Top] press

REAL Default:

0.D0

Target pressure [KBar] in a variable-cell md or relaxation run.

[Back to Top] wmass

REAL Default:

0.75*Tot_Mass/pi**2 for Parrinello-Rahman MD; 0.75*Tot_Mass/pi**2 /Omega**(2/3) for Wentzcovitch MD

Fictitious cell mass [amu] for variable-cell simulations (both 'vc-md' and 'vc-relax')

[Back to Top] cell_factor Default:

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REAL 1.2D0



Used in the construction of the pseudopotential tables. It should exceed the maximum linear contraction of the cell during a simulation.

[Back to Top] press_conv_thr REAL Default:

0.5D0 Kbar

Convergence threshold on the pressure for variable cell relaxation ('vc-relax' : note that the other convergence thresholds for ionic relaxation apply as well).

[Back to Top] cell_dofree

CHARACTER

Default:

'all'

Select which of the cell parameters should be moved: all x y z xy xz yz xyz shape volume 2Dxy 2Dshape

= = = = = = = = = = = =

all axis and angles are moved only the x component of axis 1 (v1_x) is moved only the y component of axis 2 (v2_y) is moved only the z component of axis 3 (v3_z) is moved only v1_x and v2_y are moved only v1_x and v3_z are moved only v2_y and v3_z are moved only v1_x, v2_y, v3_z are moved all axis and angles, keeping the volume fixed the volume changes, keeping all angles fixed (i.e. only celldm(1) changes) only x and y components are allowed to change as above, keeping the area in xy plane fixed

BEWARE: if axis are not orthogonal, some of these options do not work (symmetry is broken). If you are not happy with them, edit subroutine init_dofree in file Modules/cell_base.f90

[Back to Top]

Card: ATOMIC_SPECIES Syntax: ATOMIC_SPECIES X(1) Mass_X(1) PseudoPot_X(1) X(2) Mass_X(2) PseudoPot_X(2) ... X(ntyp) Mass_X(ntyp) PseudoPot_X(ntyp)

Description of items: X

CHARACTER label of the atom. Acceptable syntax: chemical symbol X (1 or 2 characters, case-insensitive) or chemical symbol plus a number or a letter, as in "Xn" (e.g. Fe1) or "X_*" or "X-*" (e.g. C1, C_h; max total length cannot exceed 3 characters)

[Back to Top] Mass_X

REAL

mass of the atomic species [amu: mass of C = 12] Used only when performing Molecular Dynamics run or structural optimization runs using Damped MD. Not actually used in all other cases (but stored in data files, so phonon calculations will use these values unless other values are provided)

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[Back to Top] PseudoPot_X CHARACTER File containing PP for this species. The pseudopotential file is assumed to be in the new UPF format. If it doesn't work, the pseudopotential format is determined by the file name: *.vdb or *.van *.RRKJ3 none of the above

Vanderbilt US pseudopotential code Andrea Dal Corso's code (old format) old PWscf norm-conserving format

[Back to Top]

Card: ATOMIC_POSITIONS { alat | bohr | angstrom | crystal | crystal_sg } IF calculation == 'bands' OR calculation == 'nscf' : Specified atomic positions will be IGNORED and those from the previous scf calculation will be used instead !!!

ELSEIF :

Syntax: ATOMIC_POSITIONS { alat | bohr | angstrom | crystal | crystal_sg } X(1) x(1) y(1) z(1) { if_pos(1)(1) if_pos(2)(1) if_pos(3)(1) } X(2) x(2) y(2) z(2) { if_pos(1)(2) if_pos(2)(2) if_pos(3)(2) } ... X(nat) x(nat) y(nat) z(nat) { if_pos(1)(nat) if_pos(2)(nat) if_pos(3)(nat) }

Description of items: alat

: atomic positions are in cartesian coordinates, in units of the lattice parameter (either celldm(1) or A). If no option is specified, 'alat' is assumed; not specifying units is DEPRECATED and will no longer be allowed in the future

bohr

: atomic positions are in cartesian coordinate, in atomic units (i.e. Bohr radii)

angstrom: atomic positions are in cartesian coordinates, in Angstrom crystal : atomic positions are in crystal coordinates, i.e. in relative coordinates of the primitive lattice vectors as defined either in card CELL_PARAMETERS or via the ibrav + celldm / a,b,c... variables crystal_sg : atomic positions are in crystal coordinates, i.e. in relative coordinates of the primitive lattice. This option differs from the previous one because in this case only the symmetry inequivalent atoms are given. The variable space_group must indicate the space group number used to find the symmetry equivalent atoms. The other variables that control this option are uniqueb, origin_choice, and rhombohedral.

X

CHARACTER label of the atom as specified in ATOMIC_SPECIES

[Back to Top]

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x, y, z

REAL

atomic positions NOTE: each atomic coordinate can also be specified as a simple algebraic expression. To be interpreted correctly expression must NOT contain any blank space and must NOT start with a "+" sign. The available expressions are: + (plus), - (minus), / (division), * (multiplication), ^ (power) All numerical constants included are considered as double-precision numbers; i.e. 1/2 is 0.5, not zero. Other functions, such as sin, sqrt or exp are not available, although sqrt can be replaced with ^(1/2). Example: C

1/3

1/2*3^(-1/2)

0

is equivalent to C

0.333333

0.288675

0.000000

Please note that this feature is NOT supported by XCrysDen (which will display a wrong structure, or nothing at all). When atomic positions are of type crystal_sg coordinates can be given in the following three forms (Wyckoff positions): C 1a C 8g x C 24m x y The first form must be used when the Wyckoff letter determines uniquely all three coordinates, the second form when the Wyckoff letter and one coordinate are needed, the third form when one letter and two coordinates are needed. The forms: C 8g x x x C 24m x x y are not allowed, but C x x x C x x y are correct.

[Back to Top] if_pos(1), if_pos(2), if_pos(3) Default:

INTEGER

1

component i of the force for this atom is multiplied by if_pos(i), which must be either 0 or 1. Used to keep selected atoms and/or selected components fixed in MD dynamics or structural optimization run. With crystal_sg atomic coordinates the constraints are copied in all equivalent atoms.

[Back to Top]

Card: K_POINTS { tpiba | automatic | crystal | gamma | tpiba_b | crystal_b | tpiba_c | crystal_c }

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IF tpiba OR crystal OR tpiba_b OR crystal_b OR tpiba_c OR crystal_c :

Syntax: K_POINTS tpiba | crystal | tpiba_b | crystal_b | tpiba_c | crystal_c nks xk_x(1) xk_y(1) xk_z(1) wk(1) xk_x(2) xk_y(2) xk_z(2) wk(2) ... xk_x(nks) xk_y(nks) xk_z(nks) wk(nks)

ELSEIF automatic :

Syntax: K_POINTS automatic nk1 nk2 nk3 sk1 sk2 sk3 ELSEIF gamma :

Syntax: K_POINTS gamma

Description of items: tpiba

: read k-points in cartesian coordinates, in units of 2 pi/a (default)

automatic: automatically generated uniform grid of k-points, i.e, generates ( nk1, nk2, nk3 ) grid with ( sk1, sk2, sk3 ) offset. nk1, nk2, nk3 as in Monkhorst-Pack grids k1, k2, k3 must be 0 ( no offset ) or 1 ( grid displaced by half a grid step in the corresponding direction ) BEWARE: only grids having the full symmetry of the crystal work with tetrahedra. Some grids with offset may not work. crystal

: read k-points in crystal coordinates, i.e. in relative coordinates of the reciprocal lattice vectors

gamma

: use k = 0 (no need to list k-point specifications after card) In this case wavefunctions can be chosen as real, and specialized subroutines optimized for calculations at the gamma point are used (memory and cpu requirements are reduced by approximately one half).

tpiba_b

: Used for band-structure plots. k-points are in units of 2 pi/a. nks points specify nks-1 lines in reciprocal space. Every couple of points identifies the initial and final point of a line. pw.x generates N intermediate points of the line where N is the weight of the first point.

crystal_b: as tpiba_b, but k-points are in crystal coordinates. tpiba_c

: Used for band-structure contour plots. k-points are in units of 2 pi/a. nks must be 3. 3 k-points k_0, k_1, and k_2 specify a rectangle in reciprocal space of vertices k_0, k_1, k_2, k_1 + k_2 - k_0: k_0 + \alpha (k_1-k_0)+ \beta (k_2-k_0) with 0

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