Structural, electronic, and optical properties of beryllium monochalcogenides

Abstract

The results of first-principles theoretical study of the structural, electronic and optical properties of beryllium monochalcogenides BeTe, BeSe and BeS, performed using the full potential linearized augmented plane wave (FP-LAPW) method are presented. The calculated structural parameters and band gaps compare very well with previous theoretical results. The trends of the band gap pressure coefficients and volume deformation potentials for these II-VI compounds are investigated. The linear pressure coefficients for the \(\Gamma - \)X and \(\Gamma - \Gamma\) band gaps increase with decrease in anion atomic weight. The dependence of the direct and indirect band gaps on the relative change of lattice constant are found to follow almost the same type of trends in each of these compounds. The volume deformation potential (\(a_{v}^{\alpha}\)) for the direct (\(\alpha = \Gamma - \Gamma\)) and indirect (\(\alpha = \Gamma - L\)) gaps are positive, but negative for the indirect (\(\Gamma - {\rm X}\)) gap. Furthermore, \(a_{v}^{\alpha}\), for \(\alpha = \Gamma - {\rm X}\) transitions decreases with increase in anion atomic number whereas \(a_{v}^{\Gamma-\Gamma}\), increases. The optical properties have also been calculated. From the reflectivity spectra, the compounds will be useful for optical applications. The variation of the band gaps with respect to the application of pressure and the origin of some of the peaks in the optical spectra are discussed in terms the calculated electronic structure.