First-principles study of structural, elastic and lattice dynamical properties of chalcopyrite BeSiV2 and MgSiV2 (V = P, As, Sb)

• Elasticity and lattice dynamics of chalcopyrite BeSiV2 and MgSiV2 are studied.
• More pronounced tetragonal distortion and elastic anisotropy are found in MgSiV2.
• Chalcopyrite BeSiV2 and MgSiV2 are brittle and ductile materials, respectively.
• Vibrational spectra are governed by both bonding strengths and atom masses.
• Phonon frequencies and atomic displacement patterns at ΓΓ point are analyzed.

First-principles calculations of the structural, elastic and lattice dynamical properties of chalcopyrite BeSiV2 and MgSiV2 (V = P, As, Sb) have been performed within density functional theory using norm-conserving pseudopotentials and generalized-gradient approximation. The obtained equilibrium structural parameters are in good agreement with available experimental and theoretical results. Single-crystal elastic constants, linear and volume compressibilities, shear anisotropic factors, as well as polycrystalline bulk, shear and Young’s modulus and Poisson’s ratio have been predicted. Our results show that, compared with BeSiV2, more pronounced tetragonal distortion and larger elastic anisotropy in both compression and shear have been found in MgSiV2 compounds. Chalcopyrite BeSiV2 and MgSiV2 have been classified as brittle and ductile materials, respectively. Phonon dispersion relations, phonon density of states, infrared absorption spectra and Raman scattering spectra have been calculated using the linear response method. Besides, the phonon frequencies and atomic displacement patterns for Raman-active (E, B2, B1 and A1), infrared-active (E and B2), and silent (A2) modes at zone-center ΓΓ point have been analyzed in detail. The character of vibrational spectra have been found to be governed by both chemical bonding strengths and masses of structural units. Moreover, the Si–V bonding is remarkably stronger than the Mg–V bonding in MgSiV2 chalcopyrite semiconductors.