Structural, mechanical, thermal and electronic properties of novel ternary carbide Al₄Si₂C₅ under high pressure by DFT calculation

Structural, electronic, elastic and thermal properties of Al₄Si₂C₅ under constant pressure were investigated by using first-principles theory. The total volume of the cell decreased by almost 15.7% under 40 GPa which is smaller than that of Al₄SiC₄ (16%), while the linear compressibility along a-or b-axis direction showed better anti-deformation behavior than that of along c-axis direction. The peak heights of total density of state (TDOS) and partial density of state (PDOS) curves of Al₄Si₂C₅ are slightly lowered with forced high pressure. Meanwhile, the mechanical properties of Al₄Si₂C₅-like elastic constants and elastic moduli accelerate with the pressure increasing from 0 GPa to 40 GPa; the thermal expansion coefficient α increases rapidly at lower temperature and this tendency gradually approaches a linear increase when the temperature is above 1000 K. At particular temperature, α decreases continuously with the pressure accelerating. Heat capacity at constant volume (CV) with pressure was also evaluated, the results displayed that CV is sensitive with the temperature rather than the pressure. The elastic anisotropy and Debye temperature with pressure were successfully obtained and discussed.