Wannier-type atomic functions and chemical bonding in crystals

A new method of chemical bonding analysis in crystalline solids is suggested. Wannier functions centered on atoms and related to upper valence and lower conduction bands of a crystal [Wannier-type atomic orbitals (WTAO)] are proposed to play a part of atom-like functions in population analysis. A straightforward variational procedure is formulated for generation of WTAO from Bloch functions (crystalline orbitals) calculated on a basis of plane waves (PW), LCAO, or any other set of functions. The advantages of the proposed approach compared to the traditional population analysis of Mulliken or Lowdin type on the basis of atomic orbitals are discussed. The proposed approach is applied to analyze the local properties of the electronic structure of Si and GaAs crystals obtained by Hartree-Fock LCAO method. (C) 2002 Wiley Periodicals, Inc.