Electronic Structure and Chemical Bonding within MgB2 and Related Borides from First Principles

Abstract

The electronic structures of actual and hypothetical binary borides AB2 (A = Al, Mg, Li, Be, Ca) and of mixed hypothetical phases A'MgB4 (A' = Al, Li) are obtained and analyzed within the density functional theory using pseudo-potential and all-electron methods (VASP and ASW) in order to address the changes in the electronic structure within the high-temperature superconductor MgB2 by modeling isoelectronic and n/p-doping effects. From the properties of quantum mixing between respective valence states and of chemical bonding we propose an analysis of the high-temperature superconductivity within the two models, the classical one of Bardeen, Cooper and Schrieffer (BCS) and the hole superconductivity model, which is based on experimental and calculated results from the literature.