In this study, we investigate the structural, mechanical, dynamical, electronic, thermodynamic, and optical properties of KBaP using density functional theory (DFT) within the plane-wave pseudopotential method as implemented in Quantum ESPRESSO. Our structural analysis reveals that the β-phase of the halfHeusler structure is the most stable, with an equilibrium lattice parameter of 7.36 Å. Mechanical and dynamical stability are confirmed through the calculation of elastic constants and phonon dispersion, respectively. Electronic properties show that KBaP is a direct bandgap semiconductor with a bandgap of 1.30 eV at the X-X point, suggesting potential applications in optoelectronic devices. Additionally, we explore the thermodynamic and optical properties, further demonstrating the potential of KBaP in energy-related applications. Our findings provide a comprehensive understanding of KBaP, establishing it as a promising material for future technological developments.

This study analyzes the lattice dynamics of HgS under various pressures using ab initio self-consistent calculations based on the plane-wave method (PW) and generalized gradient approximation (GGA). The static study, performed by enthalpy calculations, predicts that the transition from the cinnabar phase (α-HgS) to the zinc-blende B3 (β-HgS) or wurtzite (2H) structures occurs at very low pressures, at 0.65 or 0.70 GPa, respectively. Furthermore, the transition from β-HgS to the rocksalt (B1) phase occurs at 7 GPa, and at high pressure, specifically at 110 GPa, HgS can adopt the CsCl (B2) phase. The mechanical study confirms the stability of the β and 2H phases at 0 GPa. Phonon calculations corroborate the results of the static and mechanical studies regarding stability (α→0.7GPa2H→0.9GPaβ), and the results indicate that the instabilities of the transverse acoustic (TA) modes, induced by the application of pressures of 10.5 GPa, 21 GPa, and 190 GPa, are responsible for the observed phase transitions in part of the Brillouin.