Vibrational response of strontianite at high pressures and high temperatures and construction of P-T phase diagram

Our joint high-pressure and high-temperature mid-infrared absorbance and Raman investigations on a synthetic strontianite sample led to the construction of the respective pressure-temperature P-T phase diagram (maximum P = 38 GPa, maximum T = 800K). Our results allowed for the determination of the P-T slope for the onset pressure of the aragonite Pmcn -> post-aragonite Pmmn structural transition reported in the literature, which is found to be negative and equal to Delta P/Delta T = -0.012 GPa/K. The determined SrCO3P-T phase diagram appears consistent with the respective P-T phase diagrams of relevant aragonite-type carbonates. In addition, we provide the first ever measured far-infrared absorbance spectra under pressure for the family of aragonite-type carbonates. Our complementary first-principle calculations were able to reproduce the infrared spectra of both Pmcn and Pmmn phases of strontianite.