First principle based calculations of the optoelectronic features of HgSxSe1−x, HgSxTe1−x and HgSexTe1−x alloys with GGA+U functional

Abstract

Electronic and optical features of mercury chalcogenide ternary alloys HgSxSe1−x, HgSxTe1−x and HgSexTe1−x are computed using first principle based FP-LAPW methodology employing the GGA + U functional. Structural features have been computed with Wu-Cohen (WC)-GGA functional and found that both the lattice constant and bulk modulus in each alloy system vary nonlinearly with chalcogen concentration. The incapability of Engel-Vosko (EV)-GGA and modified Becke-Johnson (mBJ) functional in calculating the correct band structures and band gaps have been resolved by employing GGA + U and it shows that each of the specimens under the alloy systems is conductor. Chemical bonding between mercury and chalcogen are covalent in nature. In case of optical transitions, the chalcogen-p of valence band as initial states and Hg-6s as well as Hg-6p states of conduction band as final states play the dominant role. In each alloy system, nature of variation of each of the static dielectric constant, static refractive index and static reflectivity with chalcogen concentration x is opposite, while critical point in each of the ε2(ω), k(ω), σ(ω) andα(ω)spectra with chalcogen concentration x is similar to the nature of variation of magnitude of negative band gap with chalcogen concentration x. Several calculated properties are found to agree well with the corresponding experimental findings.