Study of superconducting properties of orthorhombic hard monoborides MB (M = Ta, Nb, W): First-principles calculations

Abstract

In this work, we have realized a comprehensive assessment of the physical properties of MB (M = Ta, Nb, W) monoborides by conducting ab initio pseudopotential calculations based on the density functional theory with its generalized gradient approximation. According to their electronic density of states, the d-orbitals of transition metal atoms contribute most to the electronic bands of the studied monoborides near the Fermi energy level, which makes them metallic. Detailed analysis of their elastic and mechanical properties reveals that all the studied monoborides have good hardness, which makes them promising candidates for the protection of cutting and forming tools. Analysis shows that WB has an electron-phonon coupling parameter of 0.551, which is significantly more extensive than TaB and NbB (0.228 and 0.220). Its relatively large electron-phonon coupling parameter makes WB superconducting at 2.794 K, being in excellent agreement with its measured value of 2.8 K. Between the studied monoborides, only WB is a hard superconductor with a ductile character and is promising the compound for exploring exotic phenomena due to the interplay of hardness and superconductivity.