First-principles study of equilibrium properties and electronic structure of Ti3Si0.75Al0.25C2solid solution

Abstract

Based on first-principles pseudopotential total energycalculations, the effects of Al substitution in Ti3SiC2,yielding chemical formula Ti3Si0.75Al0.25C2,were studied by examining the equilibrium properties and electronic structure.The lattice configurations, cohesive energy, atomic bonding properties andbulk modulus, as well as the electronic band structure, were investigated.Firstly, we obtained the equilibrium crystal parameters that includedlattice constants, internal atomic coordinates and bond lengths. Then,the degrees of Ti–Si, Ti–C and Ti–Al covalent bondings in Ti3Si0.75Al0.25C2were illustrated and compared with the corresponding values in Ti3SiC2 andTi3AlC2compounds. Furthermore, the magnitude and anisotropy ofelectrical conductivity were discussed by investigating the densityof states and band structure. The bulk modulus of Ti3Si0.75Al0.25C2yielded a value close to that of Ti3AlC2,which indicated the high bulk modulus had been preserved. Inaddition, we predicted better oxidation resistance of Ti3Si0.75Al0.25C2than that of Ti3SiC2,and this was recently verified by an isothermal oxidation experiment of Al-cemented Ti3SiC2-basedceramic.