Stability, Mechanical Properties and Electronic Properties of X₃Si (X=V, Nb, Cr, Mo and W) from First Principles Calculations

Abstract

The transition metal silicide X3Si (X = V, Nb, Cr, Mo and W) was characterized by its low density, high melting point, high temperature hardness, high temperature resistance to wear, high temperature oxidation resistance and corrosion resistance in this paper. For the fields such as aerospace, gas turbine etc, with the application of a new generation of high temperature structural materials, transition metal silicide will be one of their candidate materials. The stability, crystal structure, mechanical properties, electronic properties, Debye temperature and hardness of X3Si(X=V, Nb, Cr, Mo and W) compounds were calculated employing electronic density functional theory (DFT) and the generalized gradient approximation (GGA). The results show that the remaining silicides have stable structures except that W3Si is a metastable structure in X3Si compounds. Based on the stress-strain theory, the bulk modulus, shear modulus, Young's modulus and Poisson's ratio of Cr3Si and Mo3Si were estimated by Voigt-Reuss-Hill method: 248.7 GPa, 158.9 GPa, 393.0 GPa, 0.24 and 249.2 GPa, 134.6 GPa, 342.1 GPa, 0.27. According to the state density (DOS) analysis, we can see that the valence band of X3Si compound is a combination of covalent bond and metal bond. The temperature of Debye of Cr3Si (645.1 K) in X3Si compound is the highest. The hardness of these silicon compounds is evaluated using a semi empirical hardness theory and the result shows that Cr3Si (10.96 GPa) is the hardest compound among them.