Electronic, elastic, and thermal properties, fracture toughness, and damage tolerance of TM 5 Si 3 B (TM = V and Nb) MAB phases

The first-principles calculations are employed herein to predict the electronic, elastic, and thermal properties, fracture toughness, and damage tolerance of TM 5 Si 3 B (TM = V and Nb) MAB phases. According to formation enthalpy, phonon dispersion and single-crystal elastic constants, V 5 Si 3 B and Nb 5 Si 3 B are thermodynamically, dynamically, and mechanically stable. Pugh's ratio, Cauchy pressure, hardness, fracture toughness, and elastic anisotropic indexes are calculated, and V 5 Si 3 B and Nb 5 Si 3 B are brittle, tolerant to damage, and elastic anisotropic. The possible cleavage plane and slip systems are the (0001) plane and < 1 1¯ 00 > |{11 2¯ 0} and < 11 2¯ 0 > |{0001}, respectively, which is determined by the strong TM II -Si, TM-B, and TM I -Si bonds parallel to the (0001) plane. Finally, lattice thermal conductivity, minimum lattice thermal conductivity, and dependence of heat capacity on temperature are predicted.