Chemical bonding and elastic properties of Ti_3AC_2 phases (A =Si, Ge, and Sn A first-principle study

摘要

The chemical bonding and elastic properties as well as the effect of atomic radii for A element in the Ti_3AC_2 phases (A =Si, Ge, and Sn) were studied by ab initio total energy calculations using plane-wave pseudopotential method based on OFT. The atomic radii of A element has a weak effect on the electronic structure. However, the bond stiffness was quantitatively examined, which shows that the bond stiffness is affected by the atomic radii of A element. The calculated results including lattice constants, internal coordinate, elastic modulus, sound velocity, and Debye temperature agree with experimental values very well. With the increase of atomic radii of A element from Si, Ge to Sn, the cohesive energy and elastic moduli as well as Debye temperature decrease, but the elastic anisotropy increases. This is related to the change of bond stiffness. It can be predicted that the fracture toughness of Ti_3SnC_2 would be comparable with that of Ti_3SiC_2 and Ti_3GeC_2.