First-principles calculations of elastic and piezoelectric constants and spontaneous polarization in Cd-IV-N2 compounds

Abstract

Density functional perturbation theory calculations are carried out for the elastic and piezoelectric constants of Cd-IV-N2 compounds, which are derived from the III-N compounds by an ordered substitution of group III elements by Cd and group-IV. The spontaneous polarizations are determined as well. Properties directly derived from the elastic constants, such as the sound velocities, Debye temperature, and polycrystalline averages, are presented. The results are compared with those of Zn-IV-N2 and group-III nitrides. Generally, the elastic constants are found to be somewhat smaller than those in corresponding Zn-IV-N2 by about 15%–25%. Clear trends with the atomic number are obtained within the series with elastic constants decreasing with the atomic number and spontaneous polarization and piezoelectric coefficients increasing with the atomic number.