From phase transitions to photonics performance: First-principles exploration of InXAl1−XP (x = 0.0 0.25, 0.5, 0.75 and 1) ternary alloys for next-generation optoelectronics

Density Functional Theory (DFT) based on the full-potential linearized augmented plane wave (FP-LAPW) method has been employed to systematically investigate the structural stability, pressure-induced phase transitions, elastic, optoelectronic, and thermal properties of AlP, InP, and their mixed alloys In_xAl_1−xP alloys (x = 0, 0.25, 0.5,0.75,1) within the WIEN2k computational framework. The exchange–correlation interactions were treated using the Wu–Cohen formulation of the generalized gradient approximation (WC-GGA) to evaluate the structural, elastic, optical, and thermal properties. For electronic properties, the PBE-GGA, WC-GGA, and the modified Becke-Johnson (mBJ) potential by Tran-Blaha were employed to enhance the accuracy of the band structure calculations.Structural stability was assessed across several crystallographic configurations, including Zinc Blende, Rock Salt, Cesium Chloride, and Wurtzite phases. The findings indicate that the Zinc Blende structure is energetically the most stable among the studied phases. The phase transition pressures were calculated and compared with available theoretical and experimental data to validate the results.The electronic structure analysis reveals that these alloys exhibit semiconducting behavior with wide band gaps, making them suitable for optoelectronic applications. Thermal properties were investigated using the quasi-harmonic Debye model, yielding comprehensive insights into the heat capacity, Debye temperature, and entropy as functions of temperature. Furthermore, the elastic constants, elastic anisotropy parameters, and detailed optical properties were computed, providing a thorough understanding of the material characteristics. These findings contribute to the fundamental knowledge and potential technological applications of In_xAl_1−xP alloys.