Ab-initio calculations of the elastic properties of Si, Ge, and GaAs

Abstract

Theoretical local-density calculations are performed using normconserving pseudopotentials with a plane-wave basis set. The recently derived “stress theorem” determines the stress from the electronic ground state of any structure with arbitrary strains and atomic displacements. Stress, force and total energy are evaluated, permitting the determination of stress-strain relations including all microscopic internal strains. We describe results of ab-initio calculations for Si, Ge, and GaAs, giving the equilibrium lattice constant, all linear elastic constants C_ij and many higher-order constants. Agreement with experiment is within a few percent, except for the internal strain parameter ζ which differs from currently accepted values.

Supported in part by ONR contract NOOO14-82-C-0244.