Revealing phase relations between Fe2B7 and FeB4 and hypothetical Fe2B7-type Ru2B7 and Os2B7: first-principles calculations

摘要

Investigation of new materials recovered using high pressure can foresee the unobservable structures and bonding of crystals. Employing first-principles calculations, we aim to provide an atomic understanding of the origin of multiple phases and mutual intergrowth for metastable iron borides. The competing FeB4 and Fe2B7 in the experiment are compared by their enthalpy and structural features. The closely similar enthalpy of Fe2B7 + B and Fe2B8 (FeB4) may explain the coexistence and tight mutual intergrowth of these two phases. The hypothetical Ru2B7 and Os2B7 are also suggested by the stability evaluations. The stable Ru2B7 and Os2B7 show an interesting metallic property and a great mechanical property due to the hybridization of metal-d and B-p orbitals and B-B covalent bonding.