Crystal structure and electronic properties of BrF under high-pressure

The bromine monofluoride (BrF)'s structural and electronic properties are widely investigated under high pressure through ab initio computations using the density functional theory. At first, five new high-pressure BrF structures are uncovered with space groups P21, Cmc21, Pmc21, P2/m, and R-3m symmetry under pressure. According to the elastic constants and phonon scattering curves, the mechanical and dynamical stability of Cmc21, Pmc21, P2/m, and R-3m structures under pressures can be demonstrated. The band structure and density of states show that the P21 and the Cmc21 structures are non-metallic. In contrast, the Pmc21, P2/m, and R-3m structures are metallic. Band structure computations indicate that the Cmc21 structure is a semiconductor containing a direct band gap (Eg) of 0.90 eV (PBE) or 2.19 eV (HSE06). The electron localization function (ELF), Crystal Orbital Hamilton Population (COHP), and charge density difference calculations indicate that the Cmc21 structure is covalent. Besides, we find that the BrF (at ambient pressure) transition temperature of 144 K (∼−129 °C) is compatible with the previous experiment that reported that the temperature when BrF precipitates into a fine yellow powder is below −130 °C. The results enrich the BrF's high-pressure phases and establish the basis for subsequent theoretical and experimental studies.