Ab initio study of M₂AlN (M = Ti, V, Cr)

We have studied M₂AlN phases, where M = Ti, V, and Cr, by means of ab initio total energy calculations. The bulk modulus of M₂AlN increases as Ti is replaced with V and Cr by 19.0% and 26.5%, respectively, which can be understood on the basis of the increased number of valence electrons filling the p-d hybridized bonding states. The bulk modulus of M ₂AlN is generally higher than that of the corresponding M ₂AlC phase, which may be explained by an extra electron in the former phases contributing to stronger chemical bonding. This work is important for fundamental understanding of elastic properties of these ternary nitrides and may inspire future experimental research.