Prediction of MAX phases, VN+1SiCN (N=1,2), from first-principles theory

We have investigated the phase stability of two MAX phases, V3SiC2 and V2SiC, by means of first-principles total-energy calculations within the generalized-gradient approximation and the projector-augmented wave method. The theoretical bulk modulus of V3SiC2 is 219 GPa, which is similar to 17% larger than that of Ti3SiC2 (187 GPa). The total-energy calculations show that V2SiC is stable with a formation energy of about 0.27 eVf.u. and that V3SiC2 is metastable (only 0.02 eVf.u. is required to stabilize this phase from its competing phases). We suggest that both these two MAX compounds should be possible to synthesize as stable (or metastable) phases using, e.g., thin-film deposition. (c) 2007 American Institute of Physics.