compression of the low pressure phase involves tilting of the tetrahedra. .... metamorphic kalsilite (i.e. K/Na molar ratio ~350) from Punalur (Kerala district in ... The elastic anisotropy is therefore unknown and the crystallographic ..... where l is the average of the lengths of the T1-O2 and T2-O2 bonds ...... 2(mean) | / Σ [ Fobs.
Paper published in American Mineralogist (MSA) DOI: http://dx.doi.org/10.2138/am.2011.3793
3/14
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
Paper published in American Mineralogist (MSA) DOI: http://dx.doi.org/10.2138/am.2011.3793
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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3/14
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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3/14
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
Paper published in American Mineralogist (MSA) DOI: http://dx.doi.org/10.2138/am.2011.3793
3/14
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
26 Always consult and cite the final, published document. See http://www.minsocam.org or GeoscienceWorld
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613 614 615 616 617 618
3/14
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
27 Always consult and cite the final, published document. See http://www.minsocam.org or GeoscienceWorld
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3/14
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
Paper published in American Mineralogist (MSA) DOI: http://dx.doi.org/10.2138/am.2011.3793
3/14
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
29 Always consult and cite the final, published document. See http://www.minsocam.org or GeoscienceWorld
Paper published in American Mineralogist (MSA) DOI: http://dx.doi.org/10.2138/am.2011.3793
3/14
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)
30 Always consult and cite the final, published document. See http://www.minsocam.org or GeoscienceWorld
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3/14
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
31 Always consult and cite the final, published document. See http://www.minsocam.org or GeoscienceWorld
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3/14
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
Always consult and cite the final, published document. See http://www.minsocam.org or GeoscienceWorld
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
Always consult and cite the final, published document. See http://www.minsocam.org or GeoscienceWorld
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
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Fe(a)
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Paper published in American Mineralogist (MSA) DOI: http://dx.doi.org/10.2138/am.2011.3793
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
3/14
Rotation angle G ( ) o
Always consult and cite the final, published document. See http://www.minsocam.org or GeoscienceWorld
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
3/14