中国科学院地球化学研究所机构知识库

Single crystals of norsethite-type carbonate BaMn(CO3)2 up to 200 μm in size were synthesized in a closed cavity under high pressure–temperature (P–T) conditions. Electron microprobe analyses revealed the composition of 49.00–49.09 wt% BaO and 22.66–22.74 wt% MnO, which correspond well to the ideal formula of Ba1.0Mn1.0(CO3)2. Accurate crystalline structural data were determined from single crystal X-ray difraction (XRD). The R3c space-group with a doubled c-axis and R3m space-group were used to refne the crystal structure of BaMn(CO3)2. It is proved that R3m is the most probable space-group for the BaMn(CO3)2 crystal structure because no superstructure refections were observed in the X-ray images. The unit cell parameters were identifed to be a=5.0827(2) Å and c=17.2797(10) Å in the rhombohedral symmetry of the R3m space-group with a fnal R-value of 0.0184. High-pressure Raman spectroscopy was performed up to 10 GPa at room temperature, and Raman band shifts (d휈i dP) were quantifed. Each Raman vibration underwent resolvable splitting and the corresponding d휈i dP showed a pronounced jump as the pressure reached 3.8 GPa arising from a pressure-induced transition.