Pressure and temperature dependence of Raman scattering of MnWO4

In situ Raman spectra of MnWO4 have been measured at high pressures up to 29.4 GPa and temperatures up to 1473 K. It is shown that a pressure-induced phase transition from the monoclinic to triclinic phase starts at about 17.7 GPa at room temperature, and the phase transition is confirmed to be reversible. A temperature induced melting from monoclinic to molten state starts at 1100 K and is completed at 1300 K. After cooling, molten MnWO4 recrystallizes into monoclinic MnWO4 crystals.