Fully analytic valence force field model for the elastic and inner elastic properties of diamond and zincblende crystals

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Researchers

Research units

  • Tyndall National Institute
  • University College Cork

Abstract

Using a valence force field model based on that introduced by Martin, we present three related methods through which we analytically determine valence force field parameters. The methods introduced allow easy derivation of valence force field parameters in terms of the Kleinman parameter ζ and bulk properties of zincblende and diamond crystals. We start with a model suited for covalent and weakly ionic materials, where the valence force field parameters are derived in terms of ζ and the bulk elastic constants C11, C12, and C44. We show that this model breaks down as the material becomes more ionic and specifically when the elastic anisotropy factor A=2C44/(C11-C12)>2. The analytic model can be stabilized for ionic materials by including Martin's electrostatic terms with effective cation and anion charges in the valence force field model. Inclusion of effective charges determined via the optical phonon mode splitting provides a stable model for all but two of the materials considered (zincblende GaN and AlN). A stable model is obtained for all materials considered by also utilizing the inner elastic constant E11 to determine the magnitude of the effective charges used in the Coulomb interaction. Test calculations show that the models describe well structural relaxation in superlattices and alloys and reproduce key phonon band structure features.

Details

Original languageEnglish
Article number094112
JournalPhysical Review B
Volume100
Issue number9
Publication statusPublished - 30 Sep 2019
MoE publication typeA1 Journal article-refereed

    Research areas

  • acoustic phonons, chemical bonding, compressive strength, crystal binding, crystal structure, elastic deformation, elastic modulus, elasticity, epitaxial strain, mechanical deformation, optical phonons, poisson ratio, shear deformation, strain, structural properties

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