Linear and nonlinear electronic response to valence modifications in covalent and ionic crystals

Abstract

The modification of chemical bonds in the isoelectronic series of $A^N{B}^{8-N}$ octet compounds is studied with the self-consistent pseudopotential method for both the zinc-blende and the rocksalt structure. For either case, the isoelectronic series is constructed by changing the core charge of the two atoms in the corresponding unit cell. Modifications of chemical bonds are studied with the use of (i) the many-electron picture where the modification of atomic cores is considered as an external perturbation to which valence electrons respond, and (ii) the one-electron picture where the electrons respond to the change of self-consistent potentials. In both cases it is found that the description of the changes of the chemical bonds requires the inclusion of nonlinear terms in the electronic response. The changes of the chemical bonding along the isoelectronic series are analyzed and compared to the findings of the dielectric theory and of the empirical pseudopotential method.