Ab Initio Calculations Of Elastic Constants And Phase Transition Of BeTe And BeSe

As semiconductors, BeTe and BeSe are the most suitable candidates for fabrication of photovoltaic devices, semiconductor lasers and light emitting diodes. Despite the technological developments of BeSe, the high pressure behavior of BeSe has been the subject of considerable attention. Many fundamental problems for BeSe under high pressure condition, such as the structural, electronic and bonding mechanisms, still remain unsolved. Recently, properties of material at high pressures and high temperatures have been the objects of intensive experimental and theoretical investigations.Firstly, the transition phase of BeTe from the ZB to the RS structure is investigated by ab initio plane-wave pseudopotential density functional theory, and the lattice constant a, the bulk modulus B₀ and the first order pressure derivative of bulk modulus B₀^' are obtained. According to the usual condition of equal enthalpies, we find that the transition from the ZB structure to the NiAs structure occurs at the pressure of 32.76 GPa, as is well consistent with the experimental data and other theoretical results.Secondly, the transition phase of BeSe from the ZB to the NiAs structures is also investigated. It is found that the transition from the ZB structure to the NiAs structure occurs at the pressure of 55.4 GPa, as is well consistent with the experimental data and other theoretical results.