Investigating Carbon Telluride Compounds via First-Principles Calculations: Structural, Property, and High-Pressure Response Analyses

The structural stability, mechanical properties, electronic transport characteristics, and phonon dynamics of three predicted C–Te compounds (CTe, CTe2, and C3Te8) under high pressure were systematically examined using first-principles calculations based on density functional theory. Among them, triclinic C3Te8 shows the lowest stability and cannot exist stably even at zero temperature and pressure. In contrast, orthorhombic CTe2 remains stable up to about 5 GPa, beyond which pressure-induced phase transition or decomposition occurs. Tetragonal CTe has the highest stability, maintaining a phonon spectrum without imaginary frequencies up to 10 GPa. Both CTe and CTe2 compounds exhibit a combination of polar covalent and van der Waals bonding. Calculations of the band structure and electron transport properties reveal that CTe is a metal, while CTe2 is a direct bandgap semiconductor with an intrinsic band gap (Eg) of 1.387 eV. With increasing pressure, CTe2 evolves from a direct to an indirect band gap semiconductor and finally metallizes. The calculated room-temperature carrier mobilities of CTe2 along the [001] direction reach 83.74 cm2/(V·s) for electrons and 368.02 cm2/(V·s) for holes, representing the maximum values for both carrier types. Furthermore, pressure-dependent infrared and Raman spectra of both CTe and CTe2 have been systematically computed, providing essential theoretical reference for subsequent experimental identification of their spectroscopic characteristics.