Prediction of stabilities, mechanical properties and electronic structures of tetragonal 3d transition metal disilicides: A first-principles investigation Original Research Article

The phase stabilities, mechanical properties and electronic structures of 3d transition metal disilicides were systematically investigated by first-principles calculations. The results indicated that the crystal volume and melting temperature of the compounds increase at first and then drop again with the filling of electrons on the bonding and anti-bonding states. For tetragonal TiSi2, NiSi2, CuSi2 and ZnSi2, the calculated formation energies and elastic constants confirmed that they are either thermodynamically unstable or mechanically unstable. According to the electronic structures, it can be identified that almost all the Si–Si (I) and Si–TM (I) bonds (type I) are stronger than the Si–TM (II) and Si–TM (II) (type II) ones. Therefore, the elastic deformation resistance along the 〈0 0 1〉 direction for the compounds are expected to be larger than those along the 〈1 0 0〉 and 〈0 1 0〉 directions, demonstrated by the calculated C11, C33, Ex (Ey) and Ez values. Despite of the elastic constants and moduli, the results also showed that the Si–Si (I) and Si–TM (I) bonds are very important for elucidating the interfacial behaviors of the {0 0 1} crystal plane. For tetragonal VSi2 and CrSi2, the Si–Si (I) bonds are half the size of the Si–TM (I) ones, leading to a preferential cleavage of the Si–TM interface, and therefore they show brittle characteristics. However, the situations in FeSi2 and CoSi2 are different. The moderate bonding strength of type I bonds and the uniform distributions of electron density on different {0 0 1} interfaces indicate that slip systems preferentially appear. Therefore, FeSi2 and CoSi2 possess excellent ductility.