Since 2015 we are working at following subproject TP2:
"Vibrational spectroscopy of carbonates at high P and T and deduced structural and thermodynamic properties"
The scientific aim of this project is to determine the phase stability of carbonates at pressures (P) up to 60 GPa and temperatures (T) up to 800 K by vibrational (FTIR- and Raman-) spectroscopy in internally heated diamond anvil cells (DAC-HT). Complementary electronic structure calculations in the framework of density-functional theory (DFT) will be performed to link the atomic and electronic structure of the respective carbonates to their vibrational and thermodynamic properties. We will investigate phase transitions of the carbonate endmembers CaCO3, FeCO3, CaMg(CO3)2 and SrCO3 as well as magnesite-siderite solid solutions.
Fig.: Characteristic Raman spectra of different CaCO3 (cc) polymorphs with increasing pressure (cc-II at 2 GPa; cc-III at 4.1 GPa; cc-IIIb from 5.1 to 11.1 GPa)