Phenomenological many-body potentials from the interstitial electron model. I. Dynamic properties of metals

Inspired by the ab initio generalized-valence-bond calculations of small metal clusters, we propose a phenomenological many-body interaction model, the interstitial electron model (IEM), for interactions of ions and electrons in metals. In this model, the valence electrons are treated as classical particles situated at the crystal lattice interstitial positions. Simple pair potentials are used for ions and interstitial electrons, allowing the inhomogeneity and anisotropy of electron density distributions to be taken into account phenomenologically. To test the efficacy and applicability of this approach, the IEM is applied to lattice dynamics in fcc metals: Cu, Ni, Ag, Au, Pd, Pt, Al, Ca, Sr, and γ-Fe. The phonon dispersion relations, densities of states, and Debye temperature are calculated and found to be in good agreement with experiments. Extension of the IEM to the construction of a new many-body potential in metals and alloys is discussed.