Electronic, elastic, and thermal properties, fracture toughness, and damage tolerance of TM5Si3B (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 TM5Si3B (TM = V and Nb) MAB phases. According to formation enthalpy, phonon dispersion and single-crystal elastic constants, V5Si3B and Nb5Si3B are thermodynamically, dynamically, and mechanically stable. Pugh's ratio, Cauchy pressure, hardness, fracture toughness, and elastic anisotropic indexes are calculated, and V5Si3B and Nb5Si3B are brittle, tolerant to damage, and elastic anisotropic. The possible cleavage plane and slip systems are the (0001) plane and |{112¯0} and |{0001}, respectively, which is determined by the strong TMII-Si, TM-B, and TMI-Si bonds parallel to the (0001) plane. Finally, lattice thermal conductivity, minimum lattice thermal conductivity, and dependence of heat capacity on temperature are predicted. •The damage tolerance and KIC of V5Si3B and Nb5Si3B are comparable to MAX phases.•The possible cleavage plane is the (0001) plane.•The possible slip systems are |{112¯0} and |{0001}.•V5Si3B and Nb5Si3B are room-temperature thermal conductors and high-temperature TBCs.