Acta Physica Sinica, Volume. 69, Issue 15, 156202-1(2020)
Fig. 1. Crystal structures of MgF2 with (a) the rutile-type phase and (b) the fluorite-type phase. The large and small spheres represent magnesium and fluorine atoms, respectively.
Fig. 2. Calculated enthalpy as a function of pressure in the framework of (a) GGA and (b) LDA for MgF2 with the rutile-type and fluorite-type structures at zero temperature. In the inset, the relative enthalpy versus pressure is presented.
Fig. 3. Calculated band structures of MgF2 using GGA method: (a) The rutile-type phases at 0 and 19.26 GPa; (b) the fluorite-type phase at 19.26 and 135 GPa.
Fig. 4. Calculated phonon spectra of MgF2 with the rutile-type phases at (a) 0 GPa and (b) 19.26 GPa and with (c) the fluorite-type phase at 135 GPa using GGA method.
Fig. 5. Pressure dependence of the elastic constants
Fig. 6. Volume ratios of MgF2 with the fluorite-type structure obtained from molecular dynamics simulations and first-principles calculations: (a) Volume ratios under different pressures at 300 K; (b) volume ratios under different temperatures at 50 GPa, where in the inset, the data at 0.1 MPa is presented.
Fig. 7. Energy as a function of primitive cell volume for MgF2 with the fluorite-type structure using GGA and LDA calculations.
Fig. 8. (a) Molar volume and (b) total energy of MgF2 with the fluorite-type structure as a function of temperature under different pressures calculated by molecular dynamics.
Fig. 9. Melting phase diagram of MgF2 with the fluorite-type structure obtained from molecular dynamics (MD) simulations, in comparison with the calculated melting phase diagram of the rocksalt phase of MgO.
Fig. 10. Predicted volume thermal expansion coefficient
Fig. 11. Predicted volume thermal expansion coefficient
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Xiao-Wei Sun, Ting Song, Zi-Jiang Liu, Gui-Xin Wan, Lei Zhang, Wen-Li Chang.
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Received: Feb. 26, 2020
Accepted: --
Published Online: Dec. 30, 2020
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