The structural, dynamical, mechanical and thermal properties of layered TiB4RM (RM = Cr, Mo, W) cemented carbides

Abstract

The TiB₄RM(RM = Cr, Mo, W) tetraborides are promising hard materials, however, other physical properties of these tetraborides are currently unknown. Here, the structural, electronic, dynamical, mechanical and thermal properties of the TiB₄RM are thoroughly investigated from the first-principles calculations. These compounds are thermodynamically, mechanically, and dynamically stable, and the sequence of stability is TiB₄Mo > TiB₄Cr > TiB₄W. These compounds are brittle-hard materials, and the order of hardness is TiB₄Cr > TiB₄Mo > TiB₄W. The TiB₄W has the highest bulk modulus, and the TiB₄Cr has the highest shear modulus and Young's modulus. The electronic density of states indicates that these compounds are metallic in nature. The electron localization function reveal that the partially metallic bonding nature in addition to covalent and ionic interactions between B and metal (Ti and RM) atoms. The thermal properties indicate that the hexagonal TiB₄Mo is more suitable for high-temperature applications due to its highest bulk modulus and lowest expansion coefficient under high temperature. In addition, the mechanical properties of TiB₄RM are compared and analyzed with those of TiB₂ and RMB₂ compounds.