Disparate atomic displacements in skutterudite-type LaFe₃CoSb₁₂, a model for thermoelectric behavior

Mean-square atomic displacements in lanthanum triiron cobalt dodecaantimonide, determined as a function of temperature using single-crystal neutron diffraction, show that the La atom exhibits an anomalously large displacement at room temperature, U_eq = 0.0196 (9) Å², because it is too small to fill the atomic cage formed by the corner-linked octahedral framework of M₄Sb₁₂, M = Fe, Co. Site-occupancy refinements show 25% vacancies on the La site and an actual Fe:Co ratio of 2.17:1. Analysis of the temperature dependence of the atomic displacements identifies a significant temperature-independent component for the La atom ascribed to static disorder, which amounts to 19% of the room-temperature value. The large-amplitude rattling of the La atom can be effectively linked to the dramatic decrease of the lattice contribution to the thermal conductivity, which is a key factor for improving the thermoelectric behavior of these materials. This ­structure-property relationship offers a new paradigm for the exploration of thermoelectric materials.

Computing details

For all compounds, data collection: UCLA Crystallographic Computing Package (Strouse 1994); cell refinement: UCLA Crystallographic Computing Package - Program Least (Strouse 1994); data reduction: UCLA Crystallographic Computing Package - Program Reduce, Lehmann-Larson algorithm (Strouse 1994); program(s) used to refine structure: GSAS (Larson & Von Dreele 1986); molecular graphics: ATOMS (Dowty 1993).

(phase1)

Crystal data

La.743Fe2.74Co1.26Sb12	Dx = 7.901 Mg m^−3
Mr = 1791.49	Neutron radiation, λ = 0.8387 Å
Cubic, Im3	Cell parameters from 31 reflections
Hall symbol: -I 2 2 3	θ = 18.2–42.6°
a = 9.0971 (6) Å	µ = 0.02 mm^−1
V = 752.85 Å^3	T = 295 K
Z = 2	Sawn parallelepiped, silver
F(000) = 20.63	3.5 × 2.5 × 2.5 mm

Data collection

Huber 4-circle, Crystal Logic Controller, Helium-3 detector, DEC Alpha computer diffractometer	θmax = 50°
Radial–scans	h = 0→16
1405 measured reflections	k = 0→16
463 independent reflections	l = 0→16
321 reflections with 0.0	3 standard reflections every 200 reflections
Rint = 0.046	intensity decay: none

Refinement

Refinement on F	0 restraints
Least-squares matrix: full	w = (2Fo/σFo^2)^2
R[F^2 > 2σ(F^2)] = 0.045	(Δ/σ)max < 0.001
wR(F^2) = 0.035	Δρmax = 1.05 e Å^−3
S = 1.31	Δρmin = −0.48 e Å^−3
321 reflections	Extinction correction: B-C type I Gaussian isotropic
13 parameters	Extinction coefficient: 2.32E-04

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
La	0.0	0.0	0.0	0.0196 (9)	.743 (17)
Fe	0.25	0.25	0.25	0.0053 (1)	.685 (8)
Co	0.25	0.25	0.25	0.0053 (1)	.315 (8)
Sb	0.0	0.33678 (9)	0.16021 (8)	0.0074 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
La	0.0197 (9)	0.0197 (9)	0.0197 (9)	0.0	0.0	0.0
Fe	0.00535 (18)	0.00535 (18)	0.00535 (18)	0.00047 (16)	0.00047 (16)	0.00047 (16)
Co	0.00535 (18)	0.00535 (18)	0.00535 (18)	0.00047 (16)	0.00047 (16)	0.00047 (16)
Sb	0.0052 (3)	0.0100 (3)	0.0070 (3)	0.0	0.0	0.0013 (3)

Geometric parameters (Å, º)

La—Sb	3.3927 (9)	Sb—Sb	2.969 (1)
Fe,Co—Sb	2.5422 (4)	Sb—Sb	3.4294 (8)
Sb—Sb	2.914 (1)
Sb—Fe,Co—Sb	95.17 (2)	Fe,Co—Sb—Fe,Co	126.91 (3)
Sb—Fe,Co—Sb	84.83 (2)

(phase2)

Crystal data

La.743Fe2.74Co1.26Sb12	Dx = 7.931 Mg m^−3
Mr = 1791.49	Neutron radiation, λ = 0.8387 Å
Cubic, Im3	Cell parameters from 31 reflections
Hall symbol: -I 2 2 3	θ = 18.2–42.6°
a = 9.0854 (11) Å	µ = 0.02 mm^−1
V = 749.95 Å^3	T = 200 K
Z = 2	Sawn parallelepiped, silver
F(000) = 20.63	3.5 × 2.5 × 2.5 mm

Data collection

Huber 4-circle, Crystal Logic Controller, Helium-3 detector, DEC Alpha computer diffractometer	θmax = 50°
Radial–scans	h = 0→16
1486 measured reflections	k = 0→16
470 independent reflections	l = 0→16
316 reflections with 0.0	3 standard reflections every 200 reflections
Rint = 0.051	intensity decay: none

Refinement

Refinement on F	0 restraints
Least-squares matrix: full	w = (2Fo/σFo^2)^2
R[F^2 > 2σ(F^2)] = 0.048	(Δ/σ)max < 0.001
wR(F^2) = 0.036	Δρmax = 0.82 e Å^−3
S = 1.34	Δρmin = −0.43 e Å^−3
316 reflections	Extinction correction: B-C type I Gaussian isotropic
11 parameters	Extinction coefficient: 2.2E-04

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
La	0.0	0.0	0.0	0.0151 (5)	.743
Fe	0.25	0.25	0.25	0.0042 (1)	.686
Co	0.25	0.25	0.25	0.0042 (1)	.314
Sb	0.0	0.33668 (9)	0.15998 (8)	0.0057 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
La	0.0152 (6)	0.0152 (6)	0.0152 (6)	0.0	0.0	0.0
Fe	0.00425 (15)	0.00425 (15)	0.00425 (15)	0.00039 (18)	0.00039 (18)	0.00039 (18)
Co	0.00425 (15)	0.00425 (15)	0.00425 (15)	0.00039 (18)	0.00039 (18)	0.00039 (18)
Sb	0.0039 (3)	0.0083 (3)	0.0049 (3)	0.0	0.0	0.0008 (3)

Geometric parameters (Å, º)

La—Sb	3.386 (1)	Sb—Sb	2.967 (1)
Fe,Co—Sb	2.5393 (4)	Sb—Sb	3.4272 (9)
Sb—Sb	2.907 (1)
Sb—Fe,Co—Sb	95.11 (2)	Fe,Co—Sb—Fe,Co	126.88 (3)
Sb—Fe,Co—Sb	84.88 (2)

(phase3)

Crystal data

La.743Fe2.74Co1.26Sb12	Dx = 7.931 Mg m^−3
Mr = 1791.49	Neutron radiation, λ = 0.8387 Å
Cubic, Im3	Cell parameters from 31 reflections
Hall symbol: -I 2 2 3	θ = 18.2–42.6°
a = 9.0857 (11) Å	µ = 0.02 mm^−1
V = 750.02 Å^3	T = 150 K
Z = 2	Sawn parallelepiped, silver
F(000) = 20.63	3.5 × 2.5 × 2.5 mm

Data collection

Huber 4-circle, Crystal Logic Controller, Helium-3 detector, DEC Alpha computer diffractometer	θmax = 50°
Radial–scans	h = 0→16
1492 measured reflections	k = 0→16
471 independent reflections	l = 0→16
318 reflections with 0.0	3 standard reflections every 200 reflections
Rint = 0.053	intensity decay: none

Refinement

Refinement on F	0 restraints
Least-squares matrix: full	w = (2Fo/σFo^2)^2
R[F^2 > 2σ(F^2)] = 0.045	(Δ/σ)max < 0.001
wR(F^2) = 0.036	Δρmax = 1.11 e Å^−3
S = 1.35	Δρmin = −0.63 e Å^−3
318 reflections	Extinction correction: B-C type I Gaussian isotropic
11 parameters	Extinction coefficient: 2.2E-04

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
La	0.0	0.0	0.0	0.0127 (5)	.743
Fe	0.25	0.25	0.25	0.0032 (1)	.686
Co	0.25	0.25	0.25	0.0032 (1)	.314
Sb	0.0	0.33659 (9)	0.15999 (9)	0.0046 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
La	0.0127 (5)	0.0127 (5)	0.0127 (5)	0.0	0.0	0.0
Fe	0.00328 (15)	0.00328 (15)	0.00328 (15)	0.00003 (17)	0.00003 (17)	0.00003 (17)
Co	0.00328 (15)	0.00328 (15)	0.00328 (15)	0.00003 (17)	0.00003 (17)	0.00003 (17)
Sb	0.0031 (3)	0.0067 (3)	0.0041 (3)	0.0	0.0	0.0002 (3)

Geometric parameters (Å, º)

La—Sb	3.3861 (9)	Sb—Sb	2.969 (1)
Fe,Co—Sb	2.5391 (4)	Sb—Sb	3.4276 (9)
Sb—Sb	2.907 (1)
Sb—Fe,Co—Sb	95.09 (2)	Fe,Co—Sb—Fe,Co	126.90 (3)
Sb—Fe,Co—Sb	84.90 (2)

(phase4)

Crystal data

La.743Fe2.74Co1.26Sb12	Dx = 7.942 Mg m^−3
Mr = 1791.49	Neutron radiation, λ = 0.8387 Å
Cubic, Im3	Cell parameters from 31 reflections
Hall symbol: -I 2 2 3	θ = 18.2–42.6°
a = 9.0813 (5) Å	µ = 0.02 mm^−1
V = 748.93 Å^3	T = 125 K
Z = 2	Sawn parallelepiped, silver
F(000) = 20.63	3.5 × 2.5 × 2.5 mm

Data collection

Huber 4-circle, Crystal Logic Controller, Helium-3 detector, DEC Alpha computer diffractometer	θmax = 50°
Radial–scans	h = 0→16
484 measured reflections	k = 0→16
337 independent reflections	l = 0→16
264 reflections with 0.0	3 standard reflections every 200 reflections
Rint = 0.024	intensity decay: none

Refinement

Refinement on F	0 restraints
Least-squares matrix: full	w = (2Fo/σFo^2)^2
R[F^2 > 2σ(F^2)] = 0.062	(Δ/σ)max < 0.001
wR(F^2) = 0.043	Δρmax = 0.44 e Å^−3
S = 1.26	Δρmin = −0.25 e Å^−3
264 reflections	Extinction correction: B-C type I Gaussian isotropic
11 parameters	Extinction coefficient: 2.5E-04

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
La	0.0	0.0	0.0	0.0107 (6)	.743
Fe	0.25	0.25	0.25	0.0030 (2)	.686
Co	0.25	0.25	0.25	0.0030 (2)	.314
Sb	0.0	0.33679 (12)	0.16008 (11)	0.0039 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
La	0.0108 (7)	0.0108 (7)	0.0108 (7)	0.0	0.0	0.0
Fe	0.0031 (2)	0.0031 (2)	0.0031 (2)	0.0002 (3)	0.0002 (3)	0.0002 (3)
Co	0.0031 (2)	0.0031 (2)	0.0031 (2)	0.0002 (3)	0.0002 (3)	0.0002 (3)
Sb	0.0027 (3)	0.0058 (3)	0.0031 (3)	0.0	0.0	0.0014 (4)

Geometric parameters (Å, º)

La—Sb	3.386 (1)	Sb—Sb	2.964 (2)
Fe,Co—Sb	2.5382 (5)	Sb—Sb	3.424 (1)
Sb—Sb	2.907 (2)
Sb—Fe,Co—Sb	95.15 (3)	Fe,Co—Sb—Fe,Co	126.88 (4)
Sb—Fe,Co—Sb	84.84 (3)

(phase5)

Crystal data

La.743Fe2.74Co1.26Sb12	Dx = 7.943 Mg m^−3
Mr = 1791.49	Neutron radiation, λ = 0.8387 Å
Cubic, Im3	Cell parameters from 31 reflections
Hall symbol: -I 2 2 3	θ = 18.2–42.6°
a = 9.0809 (4) Å	µ = 0.02 mm^−1
V = 748.83 Å^3	T = 100 K
Z = 2	Sawn parallelepiped, silver
F(000) = 20.63	3.5 × 2.5 × 2.5 mm

Data collection

Huber 4-circle, Crystal Logic Controller, Helium-3 detector, DEC Alpha computer diffractometer	θmax = 50°
Radial–scans	h = 0→16
1400 measured reflections	k = 0→16
459 independent reflections	l = 0→16
330 reflections with 0.0	3 standard reflections every 200 reflections
Rint = 0.041	intensity decay: none

Refinement

Refinement on F	0 restraints
Least-squares matrix: full	w = (2Fo/σFo^2)^2
R[F^2 > 2σ(F^2)] = 0.041	(Δ/σ)max < 0.001
wR(F^2) = 0.031	Δρmax = 0.43 e Å^−3
S = 1.23	Δρmin = −0.42 e Å^−3
330 reflections	Extinction correction: B-C type I Gaussian isotropic
11 parameters	Extinction coefficient: 2.4E-04

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
La	0.0	0.0	0.0	0.0100 (3)	.743
Fe	0.25	0.25	0.25	0.0032 (1)	.686
Co	0.25	0.25	0.25	0.0032 (1)	.314
Sb	0.0	0.33678 (7)	0.15995 (7)	0.0039 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
La	0.0100 (4)	0.0100 (4)	0.0100 (4)	0.0	0.0	0.0
Fe	0.00320 (13)	0.00320 (13)	0.00320 (13)	0.00051 (14)	0.00051 (14)	0.00051 (14)
Co	0.00320 (13)	0.00320 (13)	0.00320 (13)	0.00051 (14)	0.00051 (14)	0.00051 (14)
Sb	0.00250 (19)	0.0058 (2)	0.0032 (2)	0.0	0.0	0.0005 (2)

Geometric parameters (Å, º)

La—Sb	3.3857 (7)	Sb—Sb	2.964 (1)
Fe,Co—Sb	2.5384 (2)	Sb—Sb	3.4254 (7)
Sb—Sb	2.904 (1)
Sb—Fe,Co—Sb	95.13 (2)	Fe,Co—Sb—Fe,Co	126.84 (2)
Sb—Fe,Co—Sb	84.86 (2)

(phase6)

Crystal data

La.743Fe2.74Co1.26Sb12	Dx = 7.942 Mg m^−3
Mr = 1791.49	Neutron radiation, λ = 0.8387 Å
Cubic, Im3	Cell parameters from 31 reflections
Hall symbol: -I 2 2 3	θ = 18.2–42.6°
a = 9.0814 (5) Å	µ = 0.02 mm^−1
V = 748.95 Å^3	T = 75 K
Z = 2	Sawn parallelepiped, silver
F(000) = 20.63	3.5 × 2.5 × 2.5 mm

Data collection

Huber 4-circle, Crystal Logic Controller, Helium-3 detector, DEC Alpha computer diffractometer	θmax = 50°
Radial–scans	h = 0→16
1390 measured reflections	k = 0→16
459 independent reflections	l = 0→16
328 reflections with 0.0	3 standard reflections every 200 reflections
Rint = 0.042	intensity decay: none

Refinement

Refinement on F	0 restraints
Least-squares matrix: full	w = (2Fo/σFo^2)^2
R[F^2 > 2σ(F^2)] = 0.042	(Δ/σ)max < 0.001
wR(F^2) = 0.034	Δρmax = 0.58 e Å^−3
S = 1.36	Δρmin = −0.41 e Å^−3
328 reflections	Extinction correction: B-C type I Gaussian isotropic
11 parameters	Extinction coefficient: 2.3E-04

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
La	0.0	0.0	0.0	0.0088 (4)	.743
Fe	0.25	0.25	0.25	0.0030 (1)	.686
Co	0.25	0.25	0.25	0.0030 (1)	.314
Sb	0.0	0.33671 (8)	0.15994 (7)	0.0034 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
La	0.0089 (4)	0.0089 (4)	0.0089 (4)	0.0	0.0	0.0
Fe	0.00303 (14)	0.00303 (14)	0.00303 (14)	0.00012 (15)	0.00012 (15)	0.00012 (15)
Co	0.00303 (14)	0.00303 (14)	0.00303 (14)	0.00012 (15)	0.00012 (15)	0.00012 (15)
Sb	0.0026 (2)	0.0052 (2)	0.0024 (2)	0.0	0.0	0.0006 (2)

Geometric parameters (Å, º)

La—Sb	3.3852 (8)	Sb—Sb	2.965 (1)
Fe,Co—Sb	2.5384 (3)	Sb—Sb	3.4260 (7)
Sb—Sb	2.904 (1)
Sb—Fe,Co—Sb	95.11 (2)	Fe,Co—Sb—Fe,Co	126.86 (2)
Sb—Fe,Co—Sb	84.88 (2)

(phase7)

Crystal data

La.743Fe2.74Co1.26Sb12	Dx = 7.935 Mg m^−3
Mr = 1791.49	Neutron radiation, λ = 0.8387 Å
Cubic, Im3	Cell parameters from 31 reflections
Hall symbol: -I 2 2 3	θ = 18.2–42.6°
a = 9.0839 (6) Å	µ = 0.02 mm^−1
V = 749.57 Å^3	T = 50 K
Z = 2	Sawn parallelepiped, silver
F(000) = 20.63	3.5 × 2.5 × 2.5 mm

Data collection

Huber 4-circle, Crystal Logic Controller, Helium-3 detector, DEC Alpha computer diffractometer	θmax = 50°
Radial–scans	h = 0→16
1390 measured reflections	k = 0→16
459 independent reflections	l = 0→16
329 reflections with 0.0	3 standard reflections every 200 reflections
Rint = 0.041	intensity decay: none

Refinement

Refinement on F	0 restraints
Least-squares matrix: full	w = (2Fo/σFo^2)^2
R[F^2 > 2σ(F^2)] = 0.039	(Δ/σ)max < 0.001
wR(F^2) = 0.031	Δρmax = 0.52 e Å^−3
S = 1.24	Δρmin = −0.46 e Å^−3
329 reflections	Extinction correction: B-C type I Gaussian isotropic
11 parameters	Extinction coefficient: 2.2E-04

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
La	0.0	0.0	0.0	0.0078 (3)	.743
Fe	0.25	0.25	0.25	0.0028 (1)	.686
Co	0.25	0.25	0.25	0.0028 (1)	.314
Sb	0.0	0.33684 (7)	0.16002 (7)	0.0031 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
La	0.0078 (4)	0.0078 (4)	0.0078 (4)	0.0	0.0	0.0
Fe	0.00283 (13)	0.00283 (13)	0.00283 (13)	0.00030 (14)	0.00030 (14)	0.00030 (14)
Co	0.00283 (13)	0.00283 (13)	0.00283 (13)	0.00030 (14)	0.00030 (14)	0.00030 (14)
Sb	0.0024 (2)	0.0049 (2)	0.0022 (2)	0.0	0.0	0.0004 (2)

Geometric parameters (Å, º)

La—Sb	3.3876 (7)	Sb—Sb	2.964 (1)
Fe,Co—Sb	2.5392 (3)	Sb—Sb	3.4257 (7)
Sb—Sb	2.907 (1)
Sb—Fe,Co—Sb	95.16 (2)	Fe,Co—Sb—Fe,Co	126.85 (2)
Sb—Fe,Co—Sb	84.83 (2)

(phase8)

Crystal data

La.743Fe2.74Co1.26Sb12	Dx = 7.953 Mg m^−3
Mr = 1791.49	Neutron radiation, λ = 0.8387 Å
Cubic, Im3	Cell parameters from 31 reflections
Hall symbol: -I 2 2 3	θ = 18.2–42.6°
a = 9.0771 (4) Å	µ = 0.02 mm^−1
V = 747.89 Å^3	T = 25 K
Z = 2	Sawn parallelepiped, silver
F(000) = 20.63	3.5 × 2.5 × 2.5 mm

Data collection

Huber 4-circle, Crystal Logic Controller, Helium-3 detector, DEC Alpha computer diffractometer	θmax = 50°
Radial–scans	h = 0→16
1362 measured reflections	k = 0→16
459 independent reflections	l = 0→16
348 reflections with 0.0	3 standard reflections every 200 reflections
Rint = 0.041	intensity decay: none

Refinement

Refinement on F	0 restraints
Least-squares matrix: full	w = (2Fo/σFo^2)^2
R[F^2 > 2σ(F^2)] = 0.049	(Δ/σ)max < 0.001
wR(F^2) = 0.036	Δρmax = 0.40 e Å^−3
S = 1.39	Δρmin = −0.34 e Å^−3
348 reflections	Extinction correction: B-C type I Gaussian isotropic
11 parameters	Extinction coefficient: 1.8E-04

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
La	0.0	0.0	0.0	0.0066 (3)	.743
Fe	0.25	0.25	0.25	0.0026 (1)	.686
Co	0.25	0.25	0.25	0.0026 (1)	.314
Sb	0.0	0.33674 (8)	0.15996 (7)	0.0032 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
La	0.0066 (4)	0.0066 (4)	0.0066 (4)	0.0	0.0	0.0
Fe	0.00264 (14)	0.00264 (14)	0.00264 (14)	0.00016 (15)	0.00016 (15)	0.00016 (15)
Co	0.00264 (14)	0.00264 (14)	0.00264 (14)	0.00016 (15)	0.00016 (15)	0.00016 (15)
Sb	0.0025 (2)	0.0049 (2)	0.0021 (2)	0.0	0.0	0.0004 (2)

Geometric parameters (Å, º)

La—Sb	3.3839 (8)	Sb—Sb	2.963 (1)
Fe,Co—Sb	2.5372 (3)	Sb—Sb	3.4241 (7)
Sb—Sb	2.903 (1)
Sb—Fe,Co—Sb	95.12 (2)	Fe,Co—Sb—Fe,Co	126.86 (2)
Sb—Fe,Co—Sb	84.87 (2)

(phase9)

Crystal data

La.743Fe2.74Co1.26Sb12	Dx = 7.955 Mg m^−3
Mr = 1791.49	Neutron radiation, λ = 0.8387 Å
Cubic, Im3	Cell parameters from 31 reflections
Hall symbol: -I 2 2 3	θ = 18.2–42.6°
a = 9.0762 (12) Å	µ = 0.02 mm^−1
V = 747.67 Å^3	T = 10 K
Z = 2	Sawn parallelepiped, silver
F(000) = 20.63	3.5 × 2.5 × 2.5 mm

Data collection

Huber 4-circle, Crystal Logic Controller, Helium-3 detector, DEC Alpha computer diffractometer	θmax = 50°
Radial–scans	h = 0→16
1492 measured reflections	k = 0→16
472 independent reflections	l = 0→16
323 reflections with 0.0	3 standard reflections every 200 reflections
Rint = 0.047	intensity decay: none

Refinement

Refinement on F	0 restraints
Least-squares matrix: full	w = (2Fo/σFo^2)^2
R[F^2 > 2σ(F^2)] = 0.037	(Δ/σ)max < 0.001
wR(F^2) = 0.029	Δρmax = 0.72 e Å^−3
S = 1.16	Δρmin = −0.57 e Å^−3
323 reflections	Extinction correction: B-C type I Gaussian isotropic
11 parameters	Extinction coefficient: 3.1E-04

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
La	0.0	0.0	0.0	0.0069 (3)	.743
Fe	0.25	0.25	0.25	0.0026 (1)	.686
Co	0.25	0.25	0.25	0.0026 (1)	.314
Sb	0.0	0.33669 (7)	0.15998 (6)	0.0029 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
La	0.0069 (3)	0.0069 (3)	0.0069 (3)	0.0	0.0	0.0
Fe	0.00263 (12)	0.00263 (12)	0.00263 (12)	−0.00010 (13)	−0.00010 (13)	−0.00010 (13)
Co	0.00263 (12)	0.00263 (12)	0.00263 (12)	−0.00010 (13)	−0.00010 (13)	−0.00010 (13)
Sb	0.00188 (19)	0.0046 (2)	0.00223 (19)	0.0	0.0	0.00040 (19)

Geometric parameters (Å, º)

La—Sb	3.3833 (8)	Sb—Sb	2.964 (1)
Fe,Co—Sb	2.5368 (4)	Sb—Sb	3.4237 (8)
Sb—Sb	2.904 (1)
Sb—Fe,Co—Sb	95.12 (2)	Fe,Co—Sb—Fe,Co	126.88 (2)
Sb—Fe,Co—Sb	84.87 (2)