Phase-stability, elastic behavior and pressure

Paper published in American Mineralogist (MSA) DOI: http://dx.doi.org/10.2138/am.2011.3793

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Phase-stability, elastic behavior and pressure-induced structural evolution

34

of kalsilite: a ceramic material and high-T/high-P mineral

35 36 37

G. Diego Gatta1,2, Ross J. Angel3, Jing Zhao3, Matteo Alvaro3,

38

Nicola Rotiroti1,2, Michael A. Carpenter4 1

39 40 41 42 43 44 45 46 47

Dipartimento di Scienze della Terra, Università degli Studi di Milano, Via Botticelli 23, I-20133 Milano, Italy 2 CNR Istituto per la dinamica dei processi ambientali, Via M. Bianco 9, I-20131Milano, Italy 3 Crystallography Laboratory, Department of Geosciences, Virginia Tech, Blacksburg, VA-24060 USA 4 Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, U.K.

48

Abstract: The phase-stability, elastic behavior and pressure-induced structural evolution of a

49

natural metamorphic kalsilite from Punalur (Kerala district in southern India), with P31c symmetry

50

and a K/Na molar ratio of ~350, has been investigated by in-situ X-ray single-crystal diffraction up

51

to ~7 GPa with a diamond anvil cell under hydrostatic conditions. At high-pressure, a previously

52

unreported iso-symmetric first-order phase-transition occurs at ~3.5 GPa. The volume compression

53

of the two phases is described by 3rd-order Birch-Murnaghan Equations-of-State: V0=201.02(1)Å3,

54

KT0= 59.7(5) GPa, K’=3.5(3) for the low-P polymorph, and V0=200.1(13)Å3, KT0= 44(8) GPa,

55

K’=6.4(20) for the high-P polymorph. The pressure-induced structural evolution in kalsilite up to 7

56

GPa appears to be completely reversible. The compression of both phases involves tetrahedral

57

rotations around [0001] which close up the channels within the framework. In addition,

58

compression of the low pressure phase involves tilting of the tetrahedra. The major structural

59

change at the phase transition is an increase in the tilting of the tetrahedra, but a reversion of the

60

tetrahedral rotations to the value found at ambient conditions. This behavior is in distinct contrast to

61

that of nepheline which has a tetrahedral framework of the same topology.

62 2 Always consult and cite the final, published document. See http://www.minsocam.org or GeoscienceWorld


63

Key words:

64

CRYSTAL STRUCTURE: kalsilite.

65

XRD DATA: single-crystal, high-pressure, compressibility, structural evolution.

66

COMPRESSIBILITY MEASUREMENTS: kalsilite, single-crystal.

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67 68

Introduction

69

Kalsilite is a feldspathoid with ideal chemical formula: KAlSiO4. In Nature, kalsilite occurs mainly

70

in K-rich and silica under-saturated volcanic rocks, usually associated with olivine, melilite,

71

clinopyroxene, phlogopite, nepheline, and leucite. A few occurrences of methamorphic kalsilites

72

have also been reported (e.g. Sandiford and Santosh 1991). Experiments on the stability of

73

potassium aluminosilicates indicate that kalsilite is stable at least up 15 GPa at 1300 K, and with

74

KAlSi3O8 (hollandite-type) and K2Si4O9 (wadeite-type) phases can be considered as potential host

75

for K in anhydrous hyper-alkaline systems (Liu 1987).

76

In ceramic technology, kalsilite is used as the precursor for leucite, an important component

77

in porcelain-fused-to-metal and ceramic restoration systems (Zhang et al. 2007). Kalsilite has also

78

been proposed as a high thermal expansion ceramic for bonding to metals (Bogdanovicieni et al.

79

2008) and for the production of glass-ceramic seals for use in solid oxide fuel cells (Badding et al.

80

2009). Recently, nano-sized kalsilite has been demonstrated to show an excellent and highly

81

improved oxidation activity of carbon toward diesel soot combustion (Kimura et al. 2008). Kalsilite

82

is also used as a heterogeneous catalyst for transesterification (a process in which the organic group

83

of an ester is exchanged with the organic group of an alcohol) of soybean oil with methanol to

84

biodiesel (Wen et al. 2010).

85

The tetrahedral open-framework of kalsilite is isotypic with that of tridymite and nepheline,

86

and has topological symmetry P63/mmc. The kalsilite framework consists of (0001) sheets of

87

(ordered) AlO4 and SiO4 tetrahedra forming six-membered rings (hereafter 6mR), pointing

88

alternately up (U) and down (D) [i.e. 6mR//(0001): UDUDUD, Fig. 1]. The sheets are stacked along 3 Always consult and cite the final, published document. See http://www.minsocam.org or GeoscienceWorld


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89

the c-axis and joined through the apical O1 atoms, which formally lie on special positions on the 3-

90

fold axes. In a volcanic Na-bearing kalsilites, this bridging oxygen may be displaced from the

91

threefold axis (by up to ~0.25 Å), giving Al-O-Si bond angles 4σ(FO) wR2 (F 2) 0.1379 0.1527 0.1285 GooF 1.614 1.745 1.510 Residuals (e-/Å3) -1.02/+1.17 -1.08/+1.36 -1.09/+1.20 Notes: For all of the data collections: MoKα radiation, CCD detector type, ω/φ scan type, 60 s of exposure time per frame. The crystal of kalsilite was twinned by reticular merohedry with an (0001) twin plane, and the refined volumes of the two twin components approached 50% each at all pressures. The Flack parameter (Sheldrick 1997) is approximately x =0.5 at any pressure. At 4.62, 4.94 and 6.24 GPa, a full K site occupancy was obtained within the e.s.ds; therefore, it was fixed. Rint = Σ | Fobs2 - Fobs2(mean) | / Σ [ Fobs2 ]; R1 = Σ(|Fobs| - |Fcalc|)/Σ|Fobs|; wR2 = [Σ[w(F2obs - F2calc)2]/Σ[w(F2obs)2]]0.5, w= 1/ [σ2(Fobs2) + (0.01*P)2 ], P = (Max (Fobs2, 0) +2*Fcalc2)/3. * With the crystal in the DAC without any P-medium. † Refinements with the O1 split-site model.

570 571 572 573 574

--------------------------------------------------------------------------------------------------------------

575

Table 3. (Deposited). Atomic positions, site occupancy factor and thermal displacement

576

parameters (Å2) of kalsilite at different pressures.

577 578 579 580 581 582 583 584 585 586 587 588 24 Always consult and cite the final, published document. See http://www.minsocam.org or GeoscienceWorld


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589

Table 4. Selected bond distances (Å) and angles (°) and other structural parameters of kalsilite at

590

different pressures. The torsion angles O1-O2-O2’-O1’a

591

according to Klyne and Prelog (1960). Estimated standard deviations are in parentheses.

and O1-O2-O2’-O1’b

are defined

P (GPa) K-O2 (x 3) K-O2’ (x 3) K-O1 (x 3)

0.0001 2.958(8) 2.975(8) 2.977(1) 2.970

0.0001* 2.956(15) 2.986(16) 2.9851(8) 2.973

0.90(5) 2.926(15) 2.967(16) 2.967(1) 2.953

1.33(10) 2.876(13) 2.984(13) 2.959(2) 2.940

2.30(10) 2.864(19) 2.955(19) 2.944(2) 2.921

3.05(10) 2.831(12) 2.980(13) 2.934(2) 2.915

3.27(10) 2.863(16) 2.938(18) 2.933(2) 2.908

4.62(11) 2.683(7) 3.097(9) 2.924(3) 2.901

4.94(10) 2.697(8) 3.040(11) 2.917(2) 2.885

6.24(9) 2.674(9) 3.020(12) 2.905(1) 2.866

T1-O1 T1-O2 (x 3) O1-T1-O2 (x 3) O2-T1-O2 (x 3)

1.715(4) 1.731(3) 1.727 106.6(3) 112.2(3)

1.710 (7) 1.731(4) 1.725 106.9(7) 111.9(6)

1.707(7) 1.728(4) 1.723 106.2(7) 112.5(6)

1.705(7) 1.729(4) 1.723 109.7(6) 109.3(6)

1.694(7) 1.722(8) 1.715 109.0(9) 109.9(9)

1.693(7) 1.711(7) 1.706 104.2(5) 114.2(4)

1.694(7) 1.718(8) 1.712 104.6(7) 113.9(6)

1.650(6) 1.701(5) 1.688 98.7(3) 117.7(2)

1.658(6) 1.688(5) 1.681 100.5(4) 116.7(2)

1.656(6) 1.676(5) 1.671 101.1(4) 116.4(3)

T2-O1 T2-O2 (x 3) O1-T2-O2 (x 3) O2-T2-O2 (x 3)

1.611(4) 1.616(3) 1.615 109.3(4) 109.6(4)

1.611(7) 1.626(4) 1.622 109.1(7) 109.8(7)

1.607(7) 1.623(4) 1.619 109.7(7) 109.2(7)

1.602(7) 1.623(4) 1.618 106.1(7) 112.7(6)

1.599(7) 1.620(8) 1.614 106.6(9) 112.2(8)

1.598(7) 1.616(8) 1.611 111.5(6) 107.4(6)

1.597(8) 1.605(8) 1.602 110.8(8) 108.1(8)

1.559(6) 1.591(6) 1.583 115.7(4) 102.5(5)

1.567(6) 1.592(7) 1.586 113.2(5) 105.5(5)

1.566(6) 1.579(7) 1.576 111.8(5) 107.1(5)

T1-T2 O2-O2-O2s [6mR//(0001)] O2-O2-O2l [6mR//(0001)] O2-O1-O2 [6mR⊥(0001)] O2-O2-O1 O1-O2-O2’-O1’a O1-O2-O2’-O1’b P (GPa) K-O2 (x 3) K-O2’ (x 3) K-O1 (x 3) K-O1’ (x 3) K-O1’’ (x 3)

3.326(4) 78.4(1) 161.6(2) 107.7(3) 124.6(2) 42.1(4) 44.1(4) † 4.62(11) 2.685(7) 3.095(9) 2.63(1) 2.91(1) 3.275(6)

3.321(7) 78.4(2) 161.6(3) 107.6(4) 124.8(3) 42.5(7) 43.9(7) † 4.94(10) 2.692(8) 3.06(1) 2.62(2) 2.91(3) 3.27(1)

3.314(7) 77.2(2) 162.9(3) 107.5(4) 124.3(3) 43.1(7) 45.2(7) † 6.24(9) 2.677(8) 3.02(1) 2.54(1) 2.98(2) 3.23(1)

3.307(7) 76.3(2) 163.8(3) 107.3(5) 126.0(3) 46.3(7) 44.0(6)

3.293(7) 75.5(3) 164.5(4) 107.2(6) 125.6(4) 46.6(9) 45.0(9)

3.291(7) 76.0(2) 164.0(3) 107.4(4) 123.3(3) 42.8(6) 47.8(7)

3.291(7) 75.9(3) 164.1(4) 107.3(6) 123.5(4) 43.2(9) 47.7(9)

3.209(6) 79.3(2) 160.7(2) 106.1(3) 121.9(2) 37.7(4) 49.0(5)

3.225(6) 77.9(2) 162.1(3) 106.2(3) 122.8(3) 40.3(5) 48.8(5)

3.222(6) 77.5(2) 162.5(3) 106.0(3) 123.3(3) 41.4(5) 48.6(6)

T1-O1 (x 3) T1-O2 (x 3)

1.686(6) 1.707(5) 1.697

1.694(6) 1.697(5) 1.696

1.690(6) 1.684(5) 1.687

T2-O1 (x 3) T2-O2 (x 3)

1.593(6) 1.591(6) 1.592

1.600(6) 1.590(7) 1.595

1.600(6) 1.581(7) 1.591

T1-O1-T2 153.2(4) 153.3(5) 152.2(4) T1-T2 3.190(6) 3.205(6) 3.193(5) O2-O2-O2s [6mR//(0001)] 79.3(2) 78.2(2) 77.6(2) O2-O2-O2l [6mR//(0001)] 160.7(2) 161.8(2) 162.4(4) * With the crystal in the DAC without any P-medium. † Refinements with the O1 split-site model.

592 593 594 595

25 Always consult and cite the final, published document. See http://www.minsocam.org or GeoscienceWorld


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596 597 598 599 600 601

Figure 1. Crystal structure of P31c kalsilite: (top) a single (0001) tetrahedral sheet of kalsilite, with 6mR//(0001), and (bottom) a clinographic view of the 3-dimensional framework. The dark-grey and light-gray dotted lines outline the 6mR⊥(0001) indicate the O1-O2-O2’-O1’a and O1-O2-O2’-O1’b torsion angles, respectively (Table 4).

602 603 604 605 606 607 608 609 610 611 612

T1-T2



613 614 615 616 617 618

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Figure 2. Variation of the unit-cell parameters of kalsilite with pressure. Open symbols represent data collected in decompression. The dashed and solid lines represent the axial and volume 3thorder Birch-Murnaghan EoS fits for the low-P and high-P polymorph, respectively. The e.s.ds are slightly smaller than the size of the symbols.

6195.18

8.76

5.16

620

8.70

5.14 8.64

6215.12

8.58

c (Å)

a (Å)

6225.10 5.08

623

5.06

8.34

6255.02

8.28

5.00

8.22

626

0

1

2

3

627

4

5

6

7

0

2

3

4

5

6

7

5

6

7

P (GPa) 204 202 200

629

198

1.69

196

630

194

1.68

192

3

V (Å )

631

c/a

1

P (GPa)

6281.70

1.67

632

190 188 186

1.66

633

184 182

1.65

634

180 178

1.64

636

8.46 8.40

6245.04

635

8.52

0

1

2

3

4

P (GPa)

5

6

7

0

1

2

3

4

P (GPa)

637 638 639 640 641 642 643 644 645 646



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Figure 3. Volume and axial Eulerian finite strain vs normalised stress (fe-Fe plot) for kalsilite; e.s.ds. calculated according to Heinz and Jeanloz (1984) and Angel (2000), including the measured uncertainty in V0, a0 and c0. The dashed and solid lines represent the weighted linear regressions through the data points for the low-P and high-P polymorph, respectively, and the refined Fe(0) and K’ values are reported. For the high-P polymorph, strain and stress were calculated using the a0, c0 and V0 values refined with a Birch-Murnaghan EoS fit, and the error bars include the uncertainties in these values.

647 648 649 650 651 652 653 654 655 656 657 658 659

Fe (GPa)

660 661 662 663 664 665 666 667 668 669

70 68 66 64 62 60 58 56 54 52 50 48 46 44 42 40 38 36

low-P polymorph: Fe(0) = 59.8(2) GPa K' = 3.4(2)

high-P polymorph: Fe(0) = 44.6(8) GPa K' = 6.6(4)

0.000

670

0.005

0.010

0.015

0.020

671 672

70

673

68

60

85

3.05

0.040

1.51

56

1.51

2.01 2.69

80

2.62

58

2.01

3.05

75

3.53 GPa

70 65

54

679

52

680

50

681

48

682

46

684

90

Fe(c)

676

Fe(a)

62

683

0.035

95

64

675

678

0.030

100

66

674

677

0.025

fe

0.000

60

3.53 GPa

55 50 45

0.005

0.010

0.015

0.020

fe

0.025

0.030

0.035

0.040

40 0.000

0.007

0.014

0.021

0.028

0.035

0.042

0.049

fe

685 686 687 688 28 Always consult and cite the final, published document. See http://www.minsocam.org or GeoscienceWorld


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689 690 691

Figure 4. (a) A single 6mR of kalsilite viewed down [0001] with zero rotation and space group

692

symmetry P63mc, equal to the topochemical symmetry. (b) The rotated 6mR in P31c kalsilite at

693

room conditions. The rotation angle is defined as the angle between the projections on to (0001) of

694

the T1-T2 vector (solid line) and the T1-O2 and T2-O2 vectors (broken lines), and is:

695

δ = |120 - (O2-O2-O2)|/2.

696 697 698 699 700 701 702 703 704 705 706 707 708



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709

Figure 5. (a) Variation of the tetrahedral rotation angle δ, determined from the O2-O2-O2 angles. (b) Solid symbols are the variation of the tetrahedral tilt angle φ, determined from the T1-T2 distances assuming that the sum of the T1-O1 and T2-O1 distances is 3.35 Å. Open symbols are the tilt angles from the refinements of the split-site model for O1 in the high-pressure phase. The difference between these indicates that the T-O1 bond lengths have been compressed in the highpressure phase. The vertical broken line indicates the approximate phase-transition pressure.

o

Rotation angle δ ( )

22.5

(a)

22.0 21.5 21.0 20.5 20.0 16

o

Tilt angle φ ( )

710 711 712 713 714 715 716

(b)

14

12 10 8 0

1

2

3

4

5

6

7

P (GPa)



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717

Figure 6. Evolution of the T1-O2 and T2-O2 bond distance with P. Open symbol: O1 site-split

718

model. The vertical broken line indicates the approximate phase-transition pressure.

719 1.744

720

1.632

1.736 1.624

721

724

1.720

1.616

1.712

1.608

T2-O2 (Å)

723

T1-O2 (Å)

722

1.728

1.704 1.696 1.688

1.576

1.672 1.664

726

1.592 1.584

1.680

725

1.600

1.568 0

1

2

3

4

P (GPa)

5

6

7

0

1

2

3

4

5

6

7

P (GPa)

727 728 729 730 731 732 733 734 735



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T1-T2

Always consult and cite the final, published document. See http://www.minsocam.org or GeoscienceWorld

1.64

1.65

1.66

1.67

1.68

1.69

1.70

5.00

5.02

5.04

5.06

5.08

5.10

5.12

5.14

5.16

0

0

1

1

2

2

3

3

4


P (GPa)

4

P (GPa)

5

5

6

6

7

7

3

a (Å)

c/a

c (Å) V (Å )

5.18

178

180

182

184

186

188

190

192

194

196

198

200

202

204

8.22

8.28

8.34

8.40

8.46

8.52

8.58

8.64

8.70

8.76

0

0

1

1

2

2

3

3

4

P (GPa)

4

P (GPa)

5

5

6

6

7

7

Paper published in American Mineralogist (MSA) DOI: http://dx.doi.org/10.2138/am.2011.3793 3/14


0.005

0.010

2.01

Fe (GPa) 1.51

0.015

fe

0.020

3.53 GPa

3.05 2.62

0.025

0.005

0.030

0.010

0.035

0.015

0.040

40 0.000

45

50

55

60

65

70

75

80

85

90

95

0.035

0.014

0.021

3.53 GPa

3.05

2.01 2.69

0.030

0.007

1.51

0.025

fe 100

0.020

fe

0.028

0.040

0.035

0.042

0.049

DOI: http://dx.doi.org/10.2138/am.2011.3793

0.000

46

48

50

52

54

56

58

60

62

64

66

68

70

0.000

high-P polymorph: Fe(0) = 44.6(8) GPa K' = 6.6(4)

low-P polymorph: Fe(0) = 59.8(2) GPa K' = 3.4(2)

Fe(c)

70 68 66 64 62 60 58 56 54 52 50 48 46 44 42 40 38 36

Paper published in American Mineralogist (MSA) 3/14

Fe(a)



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P (GPa)

0 8

10

16

20.0

20.5

21.0

21.5

22.0

12

o

22.5

14

Tilt angle I ( )

(a)

(b)

1

2

3

4

5

6

7

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Rotation angle G ( ) o


Paper published in American Mineralogist (MSA)

4 3 1.568

1.576

1.584

1.592

1.600

1.608

1.616

1.624

1.632

0

1

2

P (GPa)

5

6

7

DOI: http://dx.doi.org/10.2138/am.2011.3793

1.664

1.672

1.680

1.688

1.696

1.704

1.712

1.720

1.728

1.736

1.744

0

1

2

3

4

P (GPa)

5

6

7

T2-O2 (Å) T1-O2 (Å) Always consult and cite the final, published document. See http://www.minsocam.org or GeoscienceWorld

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