structural elastic

Ceramics International

The influence of transition metals on the structural stability, mechanical and thermodynamics properties of Mo 5 SiB 2 is studied by the first-principles calculations. Two doped types: TM(1) model and TM(2) model are discussed. Four doped transition metals: Cr, Nb, Re and W are considered. The calculated results show that these transition metals are thermodynamic and dynamical stability in Mo 5 SiB 2 based on the doped formation energy and phonon dispersion curves. In particular, the TM(1)-doping is more thermodynamic stability than that of the TM(2)-doping because of the B-TM-B layered structure in TM(1) model. Compared to TM(2)-doped Mo 5 SiB 2 ceramics, TM(1)-doped Mo 5 SiB 2 ceramic shows the strong elastic modulus, high hardness and high Debye temperature due to the B-TM-B layered structure. The transition metal can enhance the melting point of Mo 5 SiB 2 ceramics. The high-temperature thermodynamic properties of TM-doped Mo 5 SiB 2 derive from the vibration of B atom and Si atom. The calculated results show that the elastic modulus, hardness and Debye temperature of W-doped Mo 5 SiB 2 ceramic are larger than the Mo 5 SiB 2 ceramics and the other TM-doped Mo 5 SiB 2 ceramics due to the d -state of W. Therefore, we predict that W is a useful element to improve the overall performances of Mo 5 SiB 2 ceramics.

Influence of alloying elements on the structural stability, elastic, hardness and thermodynamic properties of Mo5SiB2 from first-principles calculations