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 diffraction (XRD). The $$R\overline{3} c$$R3¯c space-group with a doubled c-axis and $$R\overline{3} m$$R3¯m space-group were used to refine the crystal structure of BaMn(CO3)2. It is proved that $$R\overline{3} m$$R3¯m is the most probable space-group for the BaMn(CO3)2 crystal structure because no superstructure reflections were observed in the X-ray images. The unit cell parameters were identified to be a = 5.0827(2) Å and c = 17.2797(10) Å in the rhombohedral symmetry of the $$R\overline{3} m$$R3¯m space-group with a final R-value of 0.0184. High-pressure Raman spectroscopy was performed up to 10 GPa at room temperature, and Raman band shifts ($$\frac{{{\text{d}}\nu_{i} }}{{{\text{d}}P}}$$dνidP) were quantified. Each Raman vibration underwent resolvable splitting and the corresponding $$\frac{{{\text{d}}\nu_{i} }}{{{\text{d}}P}}$$dνidP showed a pronounced jump as the pressure reached 3.8 GPa arising from a pressure-induced transition.

中文翻译：

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钙钛矿型 BaMn(CO3)2 的晶体结构及其压力诱导转变的拉曼光谱研究

在高压-温度 (P-T) 条件下，在封闭腔体中合成了尺寸高达 200 μm 的 Norsethite 型碳酸盐 BaMn(CO3)2 单晶。电子探针分析揭示了 49.00-49.09 wt% BaO 和 22.66-22.74 wt% MnO 的组成，这与 Ba1.0Mn1.0(CO3)2 的理想配方非常吻合。准确的晶体结构数据由单晶 X 射线衍射 (XRD) 确定。具有双 c 轴的 $$R\overline{3} c$$R3¯c 空间群和 $$R\overline{3} m$$R3¯m 空间群用于细化晶体结构BaMn(CO3)2。证明$$R\overline{3} m$$R3¯m 是BaMn(CO3)2 晶体结构最可能的空间群，因为在X 射线图像中没有观察到超结构反射。晶胞参数被确定为 a = 5.0827(2) Å 和 c = 17。2797(10) Å 在 $$R\overline{3} m$$R3¯m 空间群的菱形对称性中，最终 R 值为 0.0184。在室温下进行高达 10 GPa 的高压拉曼光谱，拉曼谱带位移 ($$\frac{{{\text{d}}\nu_{i} }}{{{\text{d}}P }}$$dνidP) 被量化。每个拉曼振动都经历了可解析的分裂，相应的 $$\frac{{{\text{d}}\nu_{i} }}{{{\text{d}}P}}$$dνidP 表现出明显的跳跃，因为由于压力引起的转变，压力达到了 3.8 GPa。