General trend of the mechanical properties of the ternary carbides M3SiC2 (M=transition metal)

We present results from first-principles calculations of ternary transition metal carbides in the M3SiC2 series (where M=early transition metal). We predict structural and mechanical properties of these new M(N+1)AX(N) phases. The bulk modulus of the ternary carbides, M3SiC2, are in the calculations found to be proportional to the bulk modulus of the corresponding binary carbides, MC. We have analyzed this behavior using a simple, nearest-neighbor bond model, as well as from first-principles total energy calculations and have found that it is caused by a considerably weaker M-Si bond compared to the M-C bond.