Superspace-group approach to the phase transition of Cu[sub 8]GeSe[sub 6]
- National Inst. for Research in Inorganic Materials, Namiki, Tsukuba (Japan)
- Univ. of Lausanne (Switzerland). Inst. of Crystallography
The high- and low-temperature forms, i.e., phase I (stable above 328 K) and phase II (stable below 328 K), of Cu[sub 8]GeSe[sub 6] have been investigated by the powder X-ray diffraction method. Cu[sub 8]GeSe[sub 6] II is hexagonal with A = 12.6438(2), C = 11.7570(1) [angstrom], Z = 6, and P6[sub 3]cm, and its structure is considered to be a superstructure of the high-temperature form, Cu[sub 8]GeSe[sub 6] I (hexagonal, a = 7.3164(4) [approx equal] A/[radical]3, c = 11.7679(7) [angstrom], Z = 2, and P6[sub 3]mc). Rietveld analysis of Cu[sub 8]GeSe[sub 6] I (350 K) and II (290 K) has been performed using diffraction data measured by a high-resolution powder diffractometer and synchrotron X-ray radiation. For Cu[sub 8]GeSe[sub 6] II, a four-dimensional superspace group for commensurate modulation, P6[sub 3]mc (1/3 1/3 0), with basic cell constants a = 7.2999, c = 11.7570 [angstrom] has been successfully applied (R[sub wp] = 0.054). The superspace-group description allows uniform treatment of both forms, and the phase transition of Cu[sub 8]GeSe[sub 6] is explained in terms of the presence and absence of commensurate modulation waves.
- OSTI ID:
- 6103655
- Journal Information:
- Journal of Solid State Chemistry, Vol. 146:2; ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
Similar Records
Long-range modulation of a composite crystal in a five-dimensional superspace
X-ray crystal-structure refinement of the nearly commensurate phase of 1T-TaS{sub 2} in (3+2)-dimensional superspace
Related Subjects
CALORIMETRY
COPPER SELENIDES
CRYSTAL STRUCTURE
EXPERIMENTAL DATA
GERMANIUM SELENIDES
LATTICE PARAMETERS
PHASE STUDIES
TEMPERATURE DEPENDENCE
X-RAY DIFFRACTION
CHALCOGENIDES
COHERENT SCATTERING
COPPER COMPOUNDS
DATA
DIFFRACTION
GERMANIUM COMPOUNDS
INFORMATION
NUMERICAL DATA
SCATTERING
SELENIDES
SELENIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
360602* - Other Materials- Structure & Phase Studies