This paper describes the structures, thermal-expansion properties and phase transitions of the trigonal forms of ZrMo
2O
8 and HfMo
2O
8. Both phases adopt a
structure at room temperature and show positive thermal expansion. Both phases also undergo a displacive phase transition at high temperature (ZrMo
2O
8 at 487 K and HfMo
2O
8 at 463 K) to a higher-symmetry structure that has lower thermal expansion. The structure of the high-temperature α′-
AMo
2O
8 form (
A = Zr and Hf) has been refined from powder diffraction data in space group
Pm1.
Supporting information
Crystal data top
? | β = 90° |
Mr = ? | γ = 120° |
?, ? | V = 1041.58 (7) Å3 |
a = 10.1367 (3) Å | Z = ? |
b = 10.1367 (3) Å | ? radiation, λ = ? Å |
c = 11.7050 (3) Å | × × mm |
α = 90° | |
Crystal data top
? | β = 90° |
Mr = ? | γ = 120° |
?, ? | V = 1041.58 (7) Å3 |
a = 10.1367 (3) Å | Z = ? |
b = 10.1367 (3) Å | ? radiation, λ = ? Å |
c = 11.7050 (3) Å | × × mm |
α = 90° | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Biso*/Beq | |
Zr1 | 0 | 0 | 0 | 0.80 (9) | |
Zr2 | 0.333333 | 0.666667 | 0.98380 (11) | 1.11 (5) | |
Mo1 | 0.32797 (18) | 0.33766 (17) | 0.15668 (4) | 0.83 (2) | |
O1 | 0.3442 (3) | 0.49829 (19) | 0.08105 (8) | 1.89 (4) | |
O2 | 0.50662 (17) | 0.3333 (3) | 0.11810 (10) | 1.38 (3) | |
O3 | 0.1785 (2) | 0.1650 (2) | 0.10359 (13) | 1.60 (5) | |
O4 | 0.33020 (16) | 0.35219 (13) | 0.29202 (5) | 1.81 (3) | |
Crystal data top
? | β = 90° |
Mr = ? | γ = 120° |
?, ? | V = 1037.33 (6) Å3 |
a = 10.1043 (3) Å | Z = ? |
b = 10.1043 (3) Å | ? radiation, λ = ? Å |
c = 11.7320 (3) Å | × × mm |
α = 90° | |
Crystal data top
? | β = 90° |
Mr = ? | γ = 120° |
?, ? | V = 1037.33 (6) Å3 |
a = 10.1043 (3) Å | Z = ? |
b = 10.1043 (3) Å | ? radiation, λ = ? Å |
c = 11.7320 (3) Å | × × mm |
α = 90° | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Biso*/Beq | |
Hf1 | 0 | 0 | 0 | 0.49 (8) | |
Hf2 | 0.333333 | 0.666667 | 0.98341 (9) | 0.38 (4) | |
Mo1 | 0.33844 (19) | 0.33762 (18) | 0.14804 (4) | 0.77 (3) | |
O1 | 0.3442 (3) | 0.5003 (2) | 0.08080 (9) | 1.82 (4) | |
O2 | 0.50901 (18) | 0.3339 (3) | 0.11666 (10) | 1.52 (4) | |
O3 | 0.1677 (2) | 0.1637 (2) | 0.10290 (14) | 1.49 (5) | |
O4 | 0.32086 (19) | 0.35254 (16) | 0.29140 (5) | 2.05 (3) | |
Crystal data top
? | β = 90° |
Mr = ? | γ = 120° |
?, ? | V = 177.41 (2) Å3 |
a = 5.8460 (3) Å | Z = ? |
b = 5.8460 (3) Å | ? radiation, λ = ? Å |
c = 5.9941 (3) Å | × × mm |
α = 90° | |
Crystal data top
? | β = 90° |
Mr = ? | γ = 120° |
?, ? | V = 177.41 (2) Å3 |
a = 5.8460 (3) Å | Z = ? |
b = 5.8460 (3) Å | ? radiation, λ = ? Å |
c = 5.9941 (3) Å | × × mm |
α = 90° | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Biso*/Beq | |
Zr1 | 0 | 0 | 0 | 0 | |
Mo1 | 0.333333 | 0.666667 | 0.29183 (9) | 0 | |
O1 | 0.16614 (7) | 0.83386 (7) | 0.19598 (12) | 0 | |
O4 | 0.333333 | 0.666667 | 0.57172 (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, 120 | 90, 90, 120 | 90, 90, 120 |
V (Å3) | 1041.58 (7) | 1037.33 (6) | 177.41 (2) |
Z | ? | ? | ? |
Radiation type | ?, λ = ? Å | ?, λ = ? Å | ?, λ = ? Å |
µ (mm−1) | ? | ? | ? |
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 Å−3) | ?, ? | ?, ? | ?, ? |