First-Principles Investigation of Structural, Electronic, Elastic, Vibrational, and Thermodynamic Properties of HgSe in Zinc Blende (B3) and Cinnabar (B9) Phases

This study presents a comprehensive first-principles investigation of HgSe in its zinc blende (B3) and high-pressure cinnabar (B9) phases, analyzing structural, electronic, elastic, vibrational, and thermodynamic properties using density functional theory. Our calculations reveal a pressure-induced B3 → B9 phase transition at 2.75 GPa (theoretical value) and 0.77 GPa (experimentally calibrated value), with the B9 phase showing anisotropic compressibility and enhanced mechanical stability. Electronic structure calculations with the B3LYP hybrid functional demonstrate that B3-HgSe is a narrow direct-gap semiconductor (0.14 eV at the Γ-point), while B9-HgSe exhibits an indirect gap (1.40 eV), both tunable under pressure. Phonon calculations confirm the dynamical stability of both phases. Thermodynamic properties reveal the B9 phase's superior thermal stability, with a Debye temperature of 162.6 K and ductile mechanical behavior. These findings provide crucial insights into HgSe's potential applications in infrared optoelectronics, pressure sensors, and topological devices, while resolving longstanding discrepancies in previous studies of this complex material system.