Calculation of cohesive and bonding properties and structural stability of semiconductors under pressure.

Christensen N.E.

Physical and chemical trends of the properties of semiconductors are studied on the basis of first-principles electronic structure calculations. Total-energy calculations for compounds under pressure and in various (hypothetical) crystal structures are performed within the local-density approximation. The self-consistent band structures are calculated by means of the LMTO method. By transformation of the orbitals to an orthogonal basis sp3 bond orders are derived, and a transformation to a tight-binding basis allows the derivation of ionicities, polarities, metallicities etc. from the first-principles potential parameters. The theoretical ionicities relate fairly well to the empirical Phillips scale, and it is shown that a critical value close to 0.8 separates the fourfold and sixfold coordinated crystal structures. Optical-phonon and 'absolute' hydrostatic deformation potentials are derived, and a simple scheme is suggested for the calculation of band lineups in semiconductor heterostructures. The band offsets are derived from the assumption of a partial alignment of the 'dielectric midgap energy' (DME) levels of the two compound semiconductors. The DME is related to the charge-neutrality points introduced by Tejedor and Flores, and by Tersoff.

Physica Scripta Volume T, 42 298-310, 1987.

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