Showing papers by "University of Antananarivo published in 1984"

Tight-binding calculation of force constants in α palladium hydrides

Abstract: A formal derivation of the force constants in pure transition metals and in transition-metal-based interstitial alloys is derived from a tight-binding description of the electronic structure of the system. This model takes into account all contributions to the energy and the self-consistent renormalization due to the energy variation on the impurity site. Charge transfer effects, i.e. electronic rearrangement around the displaced atoms, appear only up to first order in the displacement. The model is applied to pure palladium and α-PdH, and the difficulties involved in a numerical estimation are briefly outlined.

Crystal-field effect in the determination of the dipole force tensor in transition-metal based alloys

Abstract: The dipole force tensor P resulting from the presence of one impurity in transition metals is formally given in terms of the exponential fall-off with distance of the crystal field and hopping integrals of the alloy. Whereas the term arising from the variation of the crystal field integrals is generally neglected in usual calculations, the aim of the present work is to include it. A sum rule deduced from charge conservation through atomic movement leads to a relation between the variation of the tight-binding crystal-field integrals and the hopping integrals.