Effect of Mn doping on mechanical properties and electronic structure of WCoB ternary boride by first-principles calculations**Project supported by the National Key Research and Development Program, China (Grant No. 2016YFB0700503), the National High Technology Research and Development Program of China (Grant No. 2015AA034201), the Beijing Science and Technology Plan, China (Grant No. D161100002416001), the National Natural Science Foundation of China

Abstract

The first-principles calculations are performed to investigate the structural, mechanical property, hardness, and electronic structure of WCoB with 0, 8.33, 16.67, 25, and 33.33 at.% Mn doping content and W2CoB2 with 0, 10, and 20 at.% Mn doping content. The cohesive energy and formation energy indicate that all the structures can retain good structural stability. According to the calculated elastic constants, Mn is responsible for the increase of ductility and Poissonʼs ratio and the decrease of Youngʼs modulus, shear modulus, and bulk modulus. By using the population analysis and mechanical properties, the hardness is characterized through using the five hardness models and is found to decrease with the Mn doping content increasing. The calculated electronic structure indicates that the formation of a B–Mn covalent bond and a W–Mn metallic bond contribute to the decreasing of the mechanical properties.