Unveiling high-pressure investigation of BeX (X = S, se, and Te): A DFT-base exploration of phonon spectra, molecular dynamics, optical responses, and thermodynamic stability for advance optoelectronic applications

Abstract

In this study, we focus on the structure, electronic, optical and thermodynamic properties of BeX (X = S, Se, Te) under hydrostatic pressure changes from 0 to 10 GPa. The computations were made through the Generalized Gradient approximation (GGA) and Perdew-Burke-Ernzerhof functional (PBE) utilizing the CASTEP code. It was demonstrated through phonon dispersion studies that the three compounds maintain their dynamic stability at all applied pressures because imaginary frequencies were absent everywhere in the Brillouin zone. Our study revealed that pressure puts stress on all the materials studied and BeS still maintains the prevalent electronic bandgap. Different optical properties such as dielectric functions, absorption spectra, reflectivity and energy loss, were studied in detail for photon energies less than 30 eV. Analysis of optical absorption spectra indicates significant optical activity with maximum photon absorption occurring in UV region. Furthermore, thermodynamic properties like Debye temperature, heat capacity and entropy were studied. When the pressure goes up, atoms move less and therefore heat capacity decreases. When there is constant pressure, the slope of the Gibbs free energy curve tilts slightly greater which reveals a steady variation of entropy with temperature. The findings confirm that BeX (X = S, Se, Te) has enhance thermodynamic properties and Suggest promising applications in optoelectronics, thermoelectric and thermal barriers, especially in pressure dependent optoelectronic devices.