First-principles investigation of structural stability, mechanical properties and electronic structure of Ru1−xRexB2 and Re1−xRuxB2 borides

The structural stable, elastic modulus and B/G ratio of Ru1−xRexB2 and Re1−xRuxB2 borides are studied by using first-principles approach. The calculated formation enthalpies show that the Re1−xRuxB2 is more stable than that of Ru1−xRexB2. The bulk and shear modulus of Ru1−xRexB2 and Re1−xRuxB2 borides increase with increasing Re concentration. The B/G ratio of Ru1−xRexB2 increases along the Re concentration decreases. However, there is a convex hull (x = 0.25) in Re1−xRuxB2. The calculated B/G ratio of Re0.75Ru0.25B2 (1.23) is lower than that of ReB2 (1.29), indicating that the Re1−xRuxB2 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.