First-principles elastic constants and electronic structure of beryllium chalcogenides BeS, BeSe and BeTe

A theoretical study of structural, elastic and electronic properties of BeS, BeSe and BeTe is presented using the full-potential augmented plane-waves plus local orbitals (APW + lo) within density-functional theory (DFT). Results are obtained using both the local-density approximation (LDA) and the generalized gradient approximation (GGA) for the exchange-correlation potentials. The ground-state properties, like lattice constant, bulk modulus and its first derivative obtained from our calculations agree very well with experimental and other theoretical calculations. Band structures, and total valence charge densities including spin–orbit interaction are analyzed in great detail. The calculated values of the energy gaps, bandwidths, and spin–orbit splittings and the correct band degeneracies are compared to experimental and/or ab initio results. The calculated energy gap for the series of beryllium chalcogenides BeS, BeSe and BeTe is found to be indirect (Γ–X) and underestimated by about 40% for both LDA and PBE-GGA compared to experiment. We have also reported the elastic constants of these materials; the elastic constants have been derived by the stress–strain relation.