First-principles study of structural, electronic, and mechanical properties of the nanolaminate compound Ti4GeC3 under pressure

This paper investigates the pressure dependences of the structural, electronic, mechanical, and optical properties of the nanolaminate Ti4GeC3 compound using the first-principles method based on the density functional theory. The lattice parameters and atom positions of Ti4GeC3 in bulk form were predicted and show that Ti4GeC3 is more compressible in the c direction than along the a direction. The elastic constants, shear modulus and Young’s moduli of Ti4GeC3 were then calculated at various pressures. The results indicate that Ti4GeC3 is mechanically stable in the pressure range of 0–70 GPa and that its brittle-ductile transition occurs at 60 GPa. By examining the densities of states, we also found that Ti4GeC3 remains structurally stable for pressures up to 70 GPa. Moreover, the Ti–Ge bonding is softer than all the Ti–C bonding and indicates that the Ti–C bond is more resistant to deformation than the Ti–Ge bond. Finally, the reflectivity spectrum of Ti4GeC3 under various pressures was investigated. Based on the results, we found that Ti4GeC3 can be used as a coating on spacecrafts to avoid solar heating, but it is not suitable for use under high pressure conditions.