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High-resolution synchrotron radiation powder diffraction patterns of α-Fe2O3 measured between room temperature and 1100 K, i.e. above the Néel temperature TN = 950 K, have been analyzed. The integral breadths of the Bragg peaks show a hkl-dependent anisotropy, both below and above TN. This anisotropy can be quantitatively described by using a statistical peak-broadening model [Stephens (1999). J. Appl. Cryst. 32, 281]. Model calculations show that the rhombohedral α-Fe2O3 lattice is deformed and the deformation leads to a monoclinic lattice with the unique monoclinic axis along the hexagonal [110] direction both below and above TN. The monoclinic symmetry of bulk α-Fe2O3 is compatible with α-Fe2O3 nanowire growth along the [110] direction reported in Fu et al. [Chem. Phys. Lett. (2001), 350, 491].

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S2052520616017935/dq5016sup1.cif
Contains datablocks global, I, II

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S2052520616017935/dq5016Isup2.hkl
Contains datablock I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S2052520616017935/dq5016IIsup3.hkl
Contains datablock II

CCDC references: 1515808; 1515809

Computing details top

(I) top
Crystal data top
Fe2O3β = 162.4043 (3)°
Mr = 159.7V = 201.35 (1) Å3
Monoclinic, C2/cZ = 4
Hall symbol: -C 2ycF(000) = 304
a = 9.61865 (9) ÅDx = 5.268 Mg m3
b = 5.03554 (3) ÅSynchrotron radiation
c = 13.75158 (13) ÅT = 293 K
Data collection top
2θmin = 5°, 2θmax = 29.999°, 2θstep = 0.001°
Refinement top
Rp = 0.09721 parameters
Rwp = 0.1290 restraints
Rexp = 0.0940 constraints
R(F) = 0.032Weighting scheme based on measured s.u.'s
43005 data points(Δ/σ)max = 0.025
Excluded region(s): from 30 to 100.000Background function: 5 Legendre polynoms
Profile function: Pseudo-VoigtPreferred orientation correction: none
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Fe1000.14473 (3)0.0033*
O100.309 (3)0.250.0005*
O20.449 (2)0.156 (2)0.050 (2)0.0005*
(II) top
Crystal data top
Fe2O3β = 162.3508 (2)°
Mr = 159.7V = 206.97 (1) Å3
Monoclinic, C2/cZ = 4
Hall symbol: -C 2ycF(000) = 304
a = 9.68920 (8) ÅDx = 5.125 Mg m3
b = 5.08737 (2) ÅSynchrotron radiation
c = 13.84868 (11) ÅT = 1053 K
Data collection top
2θmin = 5°, 2θmax = 29.999°, 2θstep = 0.001°
Refinement top
Rp = 0.09921 parameters
Rwp = 0.1280 restraints
Rexp = 0.0860 constraints
R(F) = 0.044Weighting scheme based on measured s.u.'s
43003 data points(Δ/σ)max = 0.036
Excluded region(s): from 30 to 100.000Background function: 5 Legendre polynoms
Profile function: Pseudo-VoigtPreferred orientation correction: none
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Fe1000.14425 (3)0.0131*
O100.313 (3)0.250.0102*
O20.449 (3)0.155 (3)0.049 (2)0.0102*
 

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