Absolute deformation potentials of Al, Si, and NaCl.

Abstract

We present an approach to the calculation of absolute deformation potentials (ADP's) based on ab initio all-electron methods. The ADP of a given single-particle state is obtained from the variation of its energy between a compressed and an expanded region of the same material. Core levels are used to calculate the band offset at the compressed-expanded homojunction. We present results for a simple metal (Al), a semiconductor (Si), and an insulator (NaCl) under uniaxial strain. We find that (i) the ADP of the valence-band maximum is positive in Si, as predicted by a simple tight-binding model, but it is negative in NaCl, in conflict with tight binding; (ii) while most conduction-band states have negative ADP's, in agreement with the tight-binding picture, some conduction states have positive ADP's; (iii) core levels have nonvanishing ADP's, so they cannot be used as ``absolute'' reference energies in the presence of strain.