Theoretical investigation of structural, electronic and optical properties of (BeS)1/(BeSe)1, (BeSe)1/(BeTe)1 and (BeS)1/(BeTe)1 superlattices under pressure

Abstract

The influence of hydrostatic pressure on structural, electronic and optical properties of short period (BeS)1/(BeSe)1, (BeSe)1/(BeTe)1 and (BeS)1/(BeTe)1 superlattices, has been investigated. The lattice parameters a and c for the tetragonal unit cell obtained by total energy calculations are in good agreement with the values calculated by macroscopic elasticity theory. The (BeS)1/(BeSe)1 superlattice possesses an indirect band gap while (BeSe)1/(BeTe)1 and (BeS)1/(BeTe)1 superlattices possess a direct band gap. The pressure ranges from 0 to 47 GPa for (BeS)1/(BeSe)1, 0 to 39 GPa for (BeSe)1/(BeTe)1, and 0 to 45 GPa for (BeS)1/(BeTe)1, meanwhile the pressure dependence of the energy band gap along different symmetry directions obey the equation Egp=Eg+ap+bp2. The pressure coefficient of the indirect band gap for (BeS)1/(BeSe)1 is −22.5675 × 10−3 eV(GPa)−1, while that of the direct band gap is estimated as −25.8581 × 10−3 eV(GPa)−1 and −24.4695 × 10−3 eV(GPa)−1 for (BeSe)1/(BeTe)1 and (BeS)1/(BeTe)1, respectively. The variation of the static dielectric constant with pressure is discussed.