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This paper describes the structures, thermal-expansion properties and phase transitions of the trigonal forms of ZrMo2O8 and HfMo2O8. Both phases adopt a P\overline 3 m structure at room temperature and show positive thermal expansion. Both phases also undergo a displacive phase transition at high temperature (ZrMo2O8 at 487 K and HfMo2O8 at 463 K) to a higher-symmetry structure that has lower thermal expansion. The structure of the high-temperature α′-AMo2O8 form (A = Zr and Hf) has been refined from powder diffraction data in space group P\overline 3m1.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108768103025138/bm5004sup1.cif
Contains datablocks alpha_zrmo2o8, alpha_hfmo2o8, alphaprimezrmo2o8

Computing details top

Figures top
[Figure 1]
[Figure 2]
[Figure 3]
[Figure 4]
[Figure 5]
[Figure 6]
[Figure 7]
[Figure 8]
(alpha_zrmo2o8) top
Crystal data top
?β = 90°
Mr = ?γ = 120°
?, ?V = 1041.58 (7) Å3
a = 10.1367 (3) ÅZ = ?
b = 10.1367 (3) Å? radiation, λ = ? Å
c = 11.7050 (3) Å × × mm
α = 90°
Data collection top
h = ??l = ??
k = ??
Refinement top
Crystal data top
?β = 90°
Mr = ?γ = 120°
?, ?V = 1041.58 (7) Å3
a = 10.1367 (3) ÅZ = ?
b = 10.1367 (3) Å? radiation, λ = ? Å
c = 11.7050 (3) Å × × mm
α = 90°
Data collection top
Refinement top
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzBiso*/Beq
Zr10000.80 (9)
Zr20.3333330.6666670.98380 (11)1.11 (5)
Mo10.32797 (18)0.33766 (17)0.15668 (4)0.83 (2)
O10.3442 (3)0.49829 (19)0.08105 (8)1.89 (4)
O20.50662 (17)0.3333 (3)0.11810 (10)1.38 (3)
O30.1785 (2)0.1650 (2)0.10359 (13)1.60 (5)
O40.33020 (16)0.35219 (13)0.29202 (5)1.81 (3)
(alpha_hfmo2o8) top
Crystal data top
?β = 90°
Mr = ?γ = 120°
?, ?V = 1037.33 (6) Å3
a = 10.1043 (3) ÅZ = ?
b = 10.1043 (3) Å? radiation, λ = ? Å
c = 11.7320 (3) Å × × mm
α = 90°
Data collection top
h = ??l = ??
k = ??
Refinement top
Crystal data top
?β = 90°
Mr = ?γ = 120°
?, ?V = 1037.33 (6) Å3
a = 10.1043 (3) ÅZ = ?
b = 10.1043 (3) Å? radiation, λ = ? Å
c = 11.7320 (3) Å × × mm
α = 90°
Data collection top
Refinement top
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzBiso*/Beq
Hf10000.49 (8)
Hf20.3333330.6666670.98341 (9)0.38 (4)
Mo10.33844 (19)0.33762 (18)0.14804 (4)0.77 (3)
O10.3442 (3)0.5003 (2)0.08080 (9)1.82 (4)
O20.50901 (18)0.3339 (3)0.11666 (10)1.52 (4)
O30.1677 (2)0.1637 (2)0.10290 (14)1.49 (5)
O40.32086 (19)0.35254 (16)0.29140 (5)2.05 (3)
(alphaprimezrmo2o8) top
Crystal data top
?β = 90°
Mr = ?γ = 120°
?, ?V = 177.41 (2) Å3
a = 5.8460 (3) ÅZ = ?
b = 5.8460 (3) Å? radiation, λ = ? Å
c = 5.9941 (3) Å × × mm
α = 90°
Data collection top
h = ??l = ??
k = ??
Refinement top
Crystal data top
?β = 90°
Mr = ?γ = 120°
?, ?V = 177.41 (2) Å3
a = 5.8460 (3) ÅZ = ?
b = 5.8460 (3) Å? radiation, λ = ? Å
c = 5.9941 (3) Å × × mm
α = 90°
Data collection top
Refinement top
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzBiso*/Beq
Zr10000
Mo10.3333330.6666670.29183 (9)0
O10.16614 (7)0.83386 (7)0.19598 (12)0
O40.3333330.6666670.57172 (14)0

Experimental details

(alpha_zrmo2o8)(alpha_hfmo2o8)(alphaprimezrmo2o8)
Crystal data
Chemical formula???
Mr???
Crystal system, space group?, ??, ??, ?
Temperature (K)???
a, b, c (Å)10.1367 (3), 10.1367 (3), 11.7050 (3)10.1043 (3), 10.1043 (3), 11.7320 (3)5.8460 (3), 5.8460 (3), 5.9941 (3)
α, β, γ (°)90, 90, 12090, 90, 12090, 90, 120
V3)1041.58 (7)1037.33 (6)177.41 (2)
Z???
Radiation type?, λ = ? Å?, λ = ? Å?, λ = ? Å
µ (mm1)???
Crystal size (mm) × × × × × ×
Data collection
Diffractometer???
Absorption correction???
No. of measured, independent and
observed (?) reflections
?, ?, ? ?, ?, ? ?, ?, ?
Rint???
Refinement
R[F2 > 2σ(F2)], wR(F2), S ?, ?, ? ?, ?, ? ?, ?, ?
No. of reflections???
No. of parameters???
No. of restraints???
Δρmax, Δρmin (e Å3)?, ??, ??, ?

 

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