Many-body potentials and atomic-scale relaxations in noble-metal alloys.

We derive empirical many-body potentials for noble-metal alloy systems in the framework of the FinnisSinclair model [Philos. Mag. A 50, 45 (1984)] which is based on a second-moment approximation to the tight-binding density of states for transition metals [F. Cyrot, J. Phys. Chem. Solids 29, 1235 (1968)]. The most important extension of the model is a simple incorporation of interspecies interactions which involves fitting the alloying energies. The importance of properly accounting for the local atomic relaxations when constructing the potentials is emphasized. The observed principal features of the phase diagrams of the alloys are all well reproduced by this scheme. Furthermore, reasonable concentration dependences of the alloy lattice parameter and elastic constants are obtained. This leads us to suggest that fine details of the electronic structure may be less important in determining atomic structures than are more global parameters such as atomic sizes and binding energies. Disciplines Atomic, Molecular and Optical Physics | Engineering | Materials Science and Engineering | Metallurgy | Physics This journal article is available at ScholarlyCommons: http://repository.upenn.edu/mse_papers/237 PHYSICAL REVIEW B VOLUME 41, NUMBER 15 15 MAY 1990-II Many-body potentials anti atomic-scale relaxations in noble-metal alloys G. J. Ackland* and V. Vitek Department ofMaterials Science and Engineering, Uniuersity ofPennsyluania, Philadelphia, Pennsyluania 19104-6272 (Received 10 March 1989; revised manuscript received 30 October 1989) We derive empirical many-body potentials for noble-metal alloy systems in the framework of the Finnis-Sinclair model [Philos. Mag. A 50, 45 (1984)] which is based on a second-moment approximation to the tight-binding density of states for transition metals [F. Cyrot, J. Phys. Chem. Solids 29, 1235 {1968)]. The most important extension of the model is a simple incorporation of interspecies interactions which involves fitting the alloying energies. The importance of properly accounting for the local atomic relaxations when constructing the potentials is emphasized. The observed principal features of the phase diagrams of the alloys are all well reproduced by this scheme. Furthermore, reasonable concentration dependences of the alloy lattice parameter and elastic constants are obtained. This leads us to suggest that fine details of the electronic structure may be less important in determining atomic structures than are more global parameters such as atomic sizes and binding energies.