Ground-state structure and physical properties of YB ₃ predicted from first-principles calculations

Using the calypso algorithm with first-principles calculations, we have predicted two orthorhombic Cmmm and Pmmm structures for YB₃. The new structures are energetically much better than the previously proposed WB₃-type, ReB₃-type, FeB₃-type, and TcP₃-type structures. We find that the Cmmm phase transforms to the Pmmm phase at about 31 GPa. Subsequent calculations show that the Cmmm phase is mechanical and dynamical stable at ambient conditions. The analysis of the chemical bonding properties indicates that there are strong B-B bonds that make considerable contributions to its stability.