First-principles investigation of bandgap engineering and stability of LiBeZ (Z = P, As) half-Heusler alloys for optoelectronic and thermoelectric applications.

Heusler alloys, particularly half-Heusler (HH) compounds, exhibit exceptional potential for next-generation optoelectronic and renewable energy applications. In this study, we employ advanced density functional theory (DFT) to systematically investigate the structural, electronic, optical, thermodynamic, and thermoelectric properties of LiBeZ (Z = P/As) HH alloys. The band structure analysis using the mBJ exchange-correlation functional reveals that both LiBeP and LiBeAs exhibit indirect band gaps (1.82 eV and 1.66 eV, respectively), placing them in the ideal range for optoelectronic applications. Additionally, their broad-spectrum absorption and minimal reflectivity highlight their potential for efficient solar cells and optical sensor technologies. Moreover, as temperature rises, the enthalpy and entropy of the alloys increase, while Gibbs free energy decreases, indicating thermal stability. The alloys' heat capacity follows the Debye model, making them suitable for thermoelectric and high-temperature electronic applications. Furthermore, from the thermoelectric properties analysis, it can be conferred that these materials have a high value of ZT