First-principles investigation of structural stability, mechanical properties and electronic structure of Ru_(1-x)Re_xB_2 and Re_(1-x)Ru_xB_2 borides

摘要

The structural stable, elastic modulus and B/G ratio of Ru_(1-x)Re_xB_2 and Re_(1-x)Ru_xB_2 borides are studied by using first-principles approach. The calculated formation enthalpies show that the Re_(1-x)Ru_xB_2 is more stable than that of Ru_(1-x)Re_xB_2. The bulk and shear modulus of Ru_(1-x)Re_xB_2 and Re_(1-x)Ru_xB_2 borides increase with increasing Re concentration. The B/G ratio of Ru_(1-x)Re_xB_2 increases along the Re concentration decreases. However, there is a convex hull (x = 0.25) in Re_(1-x)Ru_xB_2. The calculated B/G ratio of Re_(0.75)Ru_(0.25)B_2 (1.23) is lower than that of ReB_2 (1.29), indicating that the Re_(1-x)Ru_xB_2 has potential binary alloy superhard materials in this region (0 < x < 0.375). This discrepancy is originated from the hybridization between Re and B atoms is stronger than between Ru and B atoms.