Crystal structure and physical properties of Mo2B: First-principle calculations

Several decades ago, Mo2B was assumed to have an Al2Cu-type structure with I4/mcm space group. Using ab initio phonon calculations, we identify the earlier proposed Al2Cu-type structure is dynamically unstable at ambient pressure. An energetically more favorable phase with the tetragonal I4/m structure was then predicted by employing frozen-phonon technique. The currently predicted I4/m phase is mechanically and dynamically stable and energetically more favorable than that of the earlier proposed Al2Cu-type structure. The electronic structures calculations indicate that Mo2B is a metal with several bands crossing the Fermi level. Our analysis indicates that the three-dimensional network of the covalent Mo-B bond is responsible for the ultra-incompressible property of Mo2B.