Lattice dynamical, elastic properties and sound velocities of γ-Si3N4

Abstract

Lattice dynamical, elastic properties and sound velocities of γ-Si₃N₄ have been calculated by using a proposed six parameter bond-bending force constant model. In this model, the potential energy of the compound γ-Si₃N₄ is expanded by using the Taylor’s expansion in the harmonic approximation. The proposed theoretical model is used to calculate the zone-centre phonon frequencies, elastic properties, sound velocities and Debye characteristic temperature for γ-Si₃N₄ and compared our results with experimental and previously calculated results available in the literature. It is found to be in good agreement with the experimental results. The significant outcome of the present work is that the octahedral bonding is stronger than that of the tetrahedral bonding.