The electronic and mechanical properties of tetragonal YB2C as explored by first-principles methods

By means of the first-principles calculations, the lattice parameters, electronic structures, phonon dispersions, and mechanical properties of the rare earth metal borocarbide YB2C have been theoretically investigated. The dynamically stability of the layered tetragonal YB2C has been evidenced based on the frozen phonon method. We have found that the covalent bonding between B-2p, C-2p and Y-5d orbitals are responsible for the strong interlayer interactions based on the calculated electronic structures and ELF images. The estimated hardness of P42/mbc-YB2C is around 23.46 GPa which is comparable with the well-known ultra-incompressible oP6-OsB2. Additionally, the analysis of the ideal shear and tensile strength of YB2C reveals the importance of covalent bonds between Y and B/C layer which help to enhance the resistance under deformation.