Tailoring the structural stability, lattice parameters, phase transition, electronic, optical, mechanical, and thermoelectric preferences of AlAs1−xBix alloys: A DFT study

Abstract

This study employs the full-potential linearized augmented plane wave (FP-LAPW) method within the density functional theory (DFT), as implemented in the WIEN2k code, to investigate the structural, electronic, optical, mechanical, and thermoelectric properties of AlAs[Formula: see text]Bi x alloys for [Formula: see text], 0.25, 0.5, 0.75, and 1. Using the Wu–Cohen Generalized Gradient approximation (WC-GGA), the studied alloys were found to be structurally stable in the zinc-blende phase. The lattice constants exhibited a progressive increase from 5.679[Formula: see text]Å to 6.359[Formula: see text]Å with increasing Bi concentration, while the bulk moduli decreased correspondingly from 71.94[Formula: see text]GPa to 43.39[Formula: see text]GPa. Investigation of electronic properties using both the KTB-mBJ [Formula: see text] PBE and EV-GGA approaches revealed a transition from an indirect band gap at [Formula: see text] to direct band gaps at higher Bi concentrations, accompanied by a systematic reduction in band gap values. In particular, the band gaps calculated using the KTB-mBJ scheme were found to be 2.145, 1.919, 1.415, 0.842, and 0.325[Formula: see text]eV for compositions [Formula: see text], 0.25, 0.5, 0.75, and 1, respectively. The optical analyses results demonstrated a redshift in the absorption edges of the alloys, indicative of their potential applicability in infrared and optoelectronic devices. Mechanical investigations confirmed that the alloys are brittle, anisotropic, and predominantly covalent in nature, with observed reductions in stiffness and hardness as Bi concentration increases. Thermoelectric performance evaluations further showed enhanced power factor values and diminished thermal conductivity with the addition of Bi. The obtained figure of merit (ZT) values for the investigated compositions were 0.77, 0.67, 0.70, 0.65, and 0.76 for [Formula: see text], 0.25, 0.5, 0.75, and 1, respectively. These findings highlight the promising potential of the studied ternary alloys for use in thermoelectric technologies due to their advantageous performance indices.