Investigations of High-Pressure Properties of MnF2 Based on the First-Principles Method

The structural, electronic, and magnetic properties of MnF2 under high pressure and high temperature are investigated based on the first-principles methods combined with the quasi-harmonic approximation and structure-search method. The obtained results using different exchange-correlation functionals lead to a band gap between 7.3 and 10 eV for rutile-type MnF2. The band gap of rutile-type MnF2 varies very slightly with pressure, giving rise to comparable pressure coefficients with the reported materials with the smallest pressure coefficient, such as diamond and SiC. At room temperature, the phase-transition sequence of rutile-type (P42/mnm) → SrI2-type (Pbca) → cotunnite-type (Pnma) can be found, and temperature will strongly affect phase-transition behaviors, which may result in the reported experimental discrepancies about high-pressure phases.