Modeling of hP3 intermetallics in space group P-3m1: Calculated powder patterns from CRYSTMET®X-ray cell data andab initiocoordinates

Autor:	J.R. Rodgers, Peter S. White, Y. Le Page
Rok vydání:	2002
Předmět:	Physics Diffraction Radiation Ab initio Type (model theory) Condensed Matter Physics Space (mathematics) Molecular physics Distortion (mathematics) Crystallography Group (periodic table) Phase (matter) General Materials Science Wyckoff positions Instrumentation
Zdroj:	Powder Diffraction. 17:165-172
ISSN:	1945-7413 0885-7156
DOI:	10.1154/1.1483322
Popis:	There are 39 CRYSTMET®entries in the hexagonal space group P-3m1 (164) reporting both distinct pure phase compounds and atomic coordinates. Having the same Wyckoff positions in the same space group as the C6 structure type, all are isopointal with it. The range of observedc/avalues extends from about 0.65 to 1.83. Three types are distinguished: Layered materials with CdI2type, the CeCd2type which is a slight distortion of the hexagonal AlB2type, and the intermediate EuGe2type made of the materials AuTe2, BaSi2, EuGe2, and SrGe2.Ab initiomodeling of the 26 entries with CdI2and EuGe2type and atomic coordinates reproduces convincingly both theirc/aaxial ratios andzcoordinates. For CoO2and SiTe2, bothc/aandzdeviate to a degree from the reported values, indicating that those materials should be reexamined for superstructures, stoichiometry, etc.Ab initiomodeling of the 11 cell-and-type entries with CdI2type and no coordinates in CRYSTMET reproduced convincingly their reported axial ratios. The X-ray cell data and theab initiozcoordinates were then used in the production of reliable calculated powder patterns for CoTe2, CrSe2, HfS2, HfSe2, HfTe2, NbTe2, SnSe2, VS2, VTe2, ZrS2, and ZrTe2. All 11 patterns have been inserted in the intense diffraction line search system of CRYSTMET operated under the Materials Toolkit. Comparison of calculated patterns for SnSe2and ZrTe2with experimental entries in the PDF exposes the complementarity of calculated and experimental powder patterns and suggests that JCPDS pattern #15-223 should be reinterpreted in terms of the CdI2structure type. The CeCd2⇔AlB2type transformation is modeled and discussed on YCd2using bothab initiomethods and a hard-sphere model. Forzab initiosolution is identical with that from the hard-sphere model while a quantum regime is predicted in the small region 0.45
Databáze:	OpenAIRE
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