Dependence of the elastic properties of the early-transition-metal monoborides on their electronic structures: A density functional theory study

We systematically investigated the crystal structure, stability, elastic properties, chemical bonding and electronic properties of the early-transition-metal monoborides (TMBs, where TM=Sc, Ti, V, Cr, Y, Zr, Nb, Mo, Hf, Mo, and W) using the ab initio calculations based on the density functional theory. The results indicated that all 11 TMBs crystallized to a CrB-type structure are thermodynamically and mechanically stable. The elastic constants were calculated using the finite strain method. The correlation between the electronic structure and elastic properties was discussed. YB was found to have high machinability (B/C44=1.73) and low hardness (C44=43 GPa). The weak interaction between the interleaved yttrium planes and weak pd bonding resulted in the good machinability of YB