Partial ordering in the section Hf5Ge4–Zr5Ge4: Crystallographic investigation and modeling based on ab initio calculations

Autor:	Norbert Ponweiser, Klaus W. Richter, Christian L. Lengauer, Piotr Warczok
Rok vydání:	2009
Předmět:	Pearson symbol Crystallography Chemistry Rietveld refinement Ab initio quantum chemistry methods Ab initio General Materials Science Density functional theory General Chemistry Condensed Matter Physics Ground state Ternary operation Solid solution
Zdroj:	Solid State Sciences. 11:395-401
ISSN:	1293-2558
Popis:	The section Hf5Ge4–Zr5Ge4 shows the existence of extended ternary solid solutions based on the binary compounds Hf5Ge4 (Pearson symbol: oP36) and Zr5Ge4 (Pearson symbol: tP36). The corresponding homogeneity ranges have been determined experimentally at 1350 °C. Partial ordering of the metal atoms at the three crystallographically independent metal sites of the structures was investigated by means of powder X-ray diffraction (XRD) followed by Rietveld refinement as well as by single crystal XRD. The two metals Hf and Zr exhibit site preferences throughout their respective homogeneity ranges. Using a simple thermodynamic model (“compound energy model”) and employing ground state energies of hypothetical ordered compounds calculated from ab initio density functional theory, the experimentally observed site fraction data were reproduced with high accuracy. The obtained Gibbs energies were furthermore used to calculate the stability ranges of the two different phases at 1350 °C. The possible benefit of this approach for the prediction of phase stability and for the Calphad-type modeling of higher-order systems is discussed.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::54cd0cb305567d408dfc0f796b5d53e7 https://doi.org/10.1016/j.solidstatesciences.2008.09.001 Zobrazit plný text záznamu Full Text from ScienceDirect