Ab initio calculations of fundamental properties of SrTe1−x O x alloys

Abstract

Structural, electronic, optical and thermodynamic properties of the SrTe 1−x O x alloys (0 ≤ x ≤ 1) in rock-salt phase are calculated using the full potential-linearized augmented plane wave (FP-LAPW) method within density functional theory. The exchange-correlation potential for structural properties was calculated by the standard local density approximation (LDA) and GGA (PBE) and the new form of GGA (WC) which is an improved form of the most popular Perdew-Burke-Ernzerhof (PBE), while for electronic properties, in addition to LDA, GGA corrections; Engel-Vosko GGA (EV-GGA) and modified Becke-Johnson (mBJ) schemes were also applied. The results show that the use of GGA (WC) in our calculations is more appropriate than GGA and LDA and gives a good description of structural properties such as lattice parameters and bulk modulus. Our investigation on the effect of composition on lattice constant, bulk modulus and band gap for ternary alloys shows almost nonlinear dependence on the composition. In addition to FP-LAPW method, the composition dependence of the refractive index and the dielectric constant was studied by different models. On the other hand, the thermodynamic stability of this alloy was investigated by calculating the excess enthalpy of mixing H m as well as the phase diagram.

First-principles calculations of inherent properties of Rb based state-of-the-art half-Heusler compounds: promising materials for renewable energy applications

“…From this table, we can see that the bandgap of all the studied materials predicted by these potential functionals is very low in comparison to previously available data [40]. Since these potential functionals underestimate the band gap, hence to achieve the bandgap of these materials comparable to the previously reported data; we have applied the Tran-Blaha modified Becke Johnson (TB-mBJ) exchange potential because it changes some of the input parameters of above discussed semilocal potentials and reproduce the bandgap near to the experimental values [53]. Table 1 shows that the values of bandgap obtained by using TB-mBJ approach are very much similar to the previously reported data.…”