PNNL

Abstract

Abstract: The possibility of a tight-binding (TB) parameterization of transition metal (TM) and noble metal clusters is investigated. An original procedure is proposed that allows one to derive the values of orthogonal-TB matrix elements reproducing the exact one-electron spectrum from an analysis of first-principles density functional calculations. The procedure is applied to selected small metals clusters: Ni-2, Pt-2, Au-2, Pt-3, Ni-13, Pt-13, and Au-13. Ni, Pt, and Au are taken as examples of first-row TM and third-row transition and noble metals. The diatomic molecules are chosen as the simplest examples of TM clusters, Pt, allows one to compare closed-shell and spin-symmetry-broken configurations, and the 13-atom clusters are representative of larger systems. With respect to the current TB parameterizations, it is found that the p-orbitals lie at higher energies (especially for third-row TMs) than usually assumed, the diagonal matrix elements among d-functions also depend on the bond directionality, and an s-orbital relaxation effect is present for third-row elements (especially Pt). The validity of the TB approach is substantially confirmed, as well as the possibility of a TV treatment of transition and noble metal clusters, provided that these effects are taken into account (e.g., more than one s-orbital should be included in the TB parameterization for platinum). (C) 2004 Wiley Periodicals, Inc.