• Ipser, Herbert
• Franzen, Hugo Fritz
• Picha, Radim
• Richter, Klaus W.

Abstract

The binary compound Hf5Ge4 (structure type Sm5Ge4, oP36, Pnma) was found to form an extended ternary solid solution Hf5-xNbxGe4 with 0 = x = 3.8. This solid solution was investigated by X-ray diffraction employing powder- as well as single crystal methods. Structure refinements at several different compositions within the phase revealed strongly preferred site occupation by Nb at the three crystallographically independent metal sites of the Sm5Ge4-type structure yielding an almost stepwise substitution mechanism of the two transition metals. Chemical bonding and site occupation are discussed on the basis of extended Hušckel calculations performed on Hf5Ge4, and site volumes (Dirichlet domains) as well as atomic orbital occupations (site potentials) are correlated with the observed substitution mechanism. A thermodynamic model based on the compound energy formalism was developed in order to link the observed substitution mechanism to thermodynamic properties (Gibbs energies) of the different sublattices formed by the crystallographically independent sites. Œ 2003 EŽditions scientifiques et meŽdicales Elsevier SAS. All rights reserved.

Topics

• compound
• single crystal
• phase
• x-ray diffraction