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The crystal structures of three polymorphs of K3GaF6 and the transition temperatures between these phases are reported for the first time. Synchrotron powder diffraction data clearly show that at 300 K α-K3GaF6 crystallizes in space group I41/a with lattice parameters of a = 19.1124 (3) Å, c = 34.4165 (6) Å, and Z = 80. The structure is based on the double perovskite but with two fifths of the GaF6 octahedra rotated by ∼45°. This phase remains stable until ∼460 K, above which it undergoes a transition to I4/m with lattice parameters of a = 13.6088 (4) Å, c = 8.6764 (3) Å, and Z = 10 at 485 K. β-K3GaF6 has a similar structure but with only one fifth of the GaF6 rotated by ∼45°. Above ∼510 K, the cubic Fm3m δ-K3GaF6 structure is stabilized, with a lattice parameter of a = 8.6649 (1) Å at 550 K. The F atoms have highly anisotropic displacement parameters which suggest dynamic octahedral tilting is occurring. This work expands the fairly small group of double perovskite compounds which display non-cooperative patterns of octahedral tilting.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S2052520620009695/je5027sup1.cif
Contains datablocks K3GaF6_alpha, K3GaF6_I4_m, K3GaF6_Fm-3m

rtv

Rietveld powder data file (CIF format) https://doi.org/10.1107/S2052520620009695/je5027K3GaF6_alphasup2.rtv
Contains datablock 300KDataCIFgenerator

rtv

Rietveld powder data file (CIF format) https://doi.org/10.1107/S2052520620009695/je5027K3GaF6_I4_msup3.rtv
Contains datablock BetaThird

rtv

Rietveld powder data file (CIF format) https://doi.org/10.1107/S2052520620009695/je5027K3GaF6_Fm-3msup4.rtv
Contains datablock HighTempK3GaF6

pdf

Portable Document Format (PDF) file https://doi.org/10.1107/S2052520620009695/je5027sup4.pdf
Table S1

CCDC references: 2016758; 2016759; 2016760

Computing details top

(K3GaF6_alpha) top
Crystal data top
F120Ga20K60c = 34.4165 (6) Å
Mr = 6020.04V = 12573.2 (4) Å3
Tetragonal, I41/aZ = 4
a = 19.1124 (3) ÅDx = 3.180 Mg m3
Data collection top
h = l =
k =
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
K10.000000.250000.3651 (11)0.0171 (14)*
K20.8898 (12)0.4468 (14)0.5118 (8)0.0171*
K30.1961 (14)0.3217 (13)0.4966 (7)0.0171*
K40.0861 (10)0.5600 (11)0.3780 (7)0.0171*
K50.2035 (13)0.3246 (14)0.3749 (8)0.0171*
K60.000000.250000.5040 (10)0.0171*
K70.9003 (11)0.4539 (11)0.3649 (7)0.0171*
K80.9280 (10)0.0938 (12)0.3212 (6)0.016 (2)*
K90.8680 (13)0.3237 (12)0.4340 (8)0.0164*
K100.000000.250000.625000.0171*
K110.6912 (14)0.8355 (12)0.7448 (7)0.0171*
K120.1663 (14)0.6827 (13)0.3051 (7)0.0164*
K130.7263 (12)0.5110 (15)0.3113 (10)0.0164*
K140.1023 (14)0.0447 (14)0.2545 (7)0.0171*
K150.000000.250000.0063 (10)0.0171*
K160.0958 (13)0.0480 (12)0.1182 (7)0.0171*
K170.000000.250000.125000.0171*
K180.0733 (10)0.9058 (12)0.9359 (9)0.0164*
Ga190.0543 (8)0.3990 (7)0.4367 (4)0.0155 (6)*
Ga200.6493 (8)0.6983 (7)0.8122 (5)0.0155*
Ga210.5502 (7)0.8987 (7)0.1882 (5)0.0155*
Ga220.2474 (8)0.5008 (7)0.0618 (5)0.0155*
Ga230.5483 (6)0.8979 (7)0.6874 (4)0.0155*
F10.107 (2)0.425 (3)0.4788 (12)0.0150 (15)*
F20.017 (2)0.378 (3)0.3967 (12)0.0150*
F30.736 (2)0.740 (2)0.8148 (17)0.0150*
F40.555 (2)0.649 (2)0.8112 (15)0.0150*
F50.636 (2)0.937 (2)0.1814 (15)0.0150*
F60.022 (2)0.4921 (19)0.4381 (17)0.0150*
F70.098 (3)0.315 (2)0.4299 (15)0.0150*
F80.606 (3)0.784 (2)0.8145 (17)0.0150*
F90.687 (2)0.6064 (19)0.8127 (17)0.0150*
F100.505 (2)0.985 (2)0.1863 (19)0.0150*
F110.554 (3)0.912 (3)0.2413 (11)0.0150*
F120.019 (2)0.371 (3)0.4743 (13)0.0150*
F130.120 (2)0.426 (2)0.3959 (12)0.0150*
F140.651 (3)0.696 (3)0.8675 (11)0.0150*
F150.660 (3)0.692 (3)0.7582 (11)0.0150*
F160.468 (2)0.848 (2)0.1861 (15)0.0150*
F170.598 (2)0.814 (2)0.1867 (17)0.0150*
F180.549 (3)0.889 (3)0.1340 (10)0.0150*
F190.279 (2)0.5946 (19)0.0640 (16)0.0150*
F200.162 (2)0.533 (2)0.0623 (16)0.0150*
F210.2579 (19)0.501 (3)0.1156 (10)0.0150*
F220.225 (2)0.402 (2)0.0684 (13)0.0150*
F230.337 (2)0.467 (2)0.0626 (15)0.0150*
F240.261 (2)0.495 (3)0.0092 (10)0.0150*
F250.629 (2)0.956 (3)0.6879 (19)0.0150*
F260.496 (2)0.982 (2)0.6918 (17)0.0150*
F270.562 (3)0.901 (3)0.7461 (10)0.0150*
F280.468 (2)0.854 (3)0.7054 (12)0.0150*
F290.600 (2)0.812 (2)0.6869 (16)0.0150*
F300.526 (2)0.894 (3)0.6360 (11)0.0150*
(K3GaF6_I4_m) top
Crystal data top
F30Ga5K15c = 8.6764 (3) Å
Mr = 1505.01V = 1606.9 (1) Å3
Tetragonal, I4/mZ = 2
a = 13.6088 (4) ÅDx = 3.111 Mg m3
Data collection top
h = l =
k =
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
K10.8033 (4)0.0972 (4)0.25000.0711 (6)*
K20.50000.00000.75000.0711*
K30.00000.00000.50000.0757 (11)*
K40.9114 (7)0.2745 (7)0.00000.0757*
Ga10.00000.00000.00000.0203 (4)*
Ga20.6996 (3)0.9003 (2)0.50000.0203*
F10.0545 (18)0.1291 (12)0.00000.0468 (9)*
F20.8443 (19)0.4690 (9)0.00000.0468*
F30.1767 (9)0.0473 (16)0.50000.0468*
F40.3144 (8)0.0651 (7)0.7089 (6)0.0468*
F50.7594 (19)0.7740 (9)0.50000.0468*
F60.8566 (16)0.4264 (9)0.50000.0468*
F70.00000.00000.2089 (6)0.0468*
(K3GaF6_Fm-3m) top
Crystal data top
F6GaK3V = 650.57 (3) Å3
Mr = 301Z = 4
Cubic, Fm3mDx = 3.073 Mg m3
a = 8.6649 (1) Å
Data collection top
h = l =
k =
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Ka0.250000.250000.250000.0737 (7)*
Kb0.000000.000000.000000.0972 (12)*
Ga0.500000.500000.500000.0209 (5)*
F0.2902 (2)0.000000.000000.121
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
F0.0285 (18)0.1670 (18)0.1670 (18)0.00000.00000.0000
 

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