For the first time, a new ordered double carbonate, BaFe(CO₃)₂, was synthesized by a solid-state reaction between BaCO₃ and FeCO₃ at high pressure-temperature conditions (PT; 3 GPa and 700 °C). This finding adds a new so-far unknown member to the group of norsethite-structured carbonates, which is often used as a geochemical analogue for dolomite. Thermogravimetric (TG) analysis and differential scanning calorimetry (DSC) reveal that BaFe(CO₃)₂ decomposes between temperatures of 450 °C and 880 °C, which is similar to norsethite (BaMg(CO₃)₂), but substantially higher than of pure FeCO₃. The formation of BaFe(CO₃)₂ through solid-state reaction is evidently slower than that of BaMg(CO₃)₂ and BaMn(CO₃)₂ under the same experimental conditions. Using synthetic BaFe(CO₃)₂ powder as starting material, the reaction in the presence of CO₂-bearing solution in contrast to water as a flux medium indicates the BaFe(CO₃)₂ instability at high PT conditions. The crystal structure and composition of the double carbonate were obtained using single crystal X-ray diffraction (XRD), Raman spectroscopy, and electron probe (EP) analysis. Two different types of the new double carbonate were identified: The experimentally derived phase belong to crystal structures that are related to the $R\overline{3}m$ and $R\overline{3}c$ space groups, respectively. The Raman spectra indicated that the difference is caused by a superstructure parallel to the c-axis. The charge and spin states of Fe in the new phases is determined using Nuclear forward scattering of synchrotron radiation. Furthermore, the thermodynamic properties of the double carbonate at standard conditions are estimated and a phase diagram is constructed depicting the stability field in low-temperature aqueous environments with these results being compared to natural aqueous solutions.

通过 BaCO ₃和 FeCO ₃在高压-温度条件（PT；3 GPa 和 700 °C）下的固态反应，首次合成了一种新的有序双碳酸盐 BaFe(CO ₃ ) ₂。这一发现为常被用作白云石地球化学类似物的北长石结构碳酸盐群增加了一个迄今为止未知的新成员。热重 (TG) 分析和差示扫描量热法 (DSC) 显示 BaFe(CO ₃ ) ₂在 450 °C 和 880 °C 之间分解，这与 Norsethite (BaMg(CO ₃ ) ₂ )相似，但显着高于纯 FeCO ₃. 在相同的实验条件下，通过固相反应形成BaFe(CO ₃ ) ₂明显慢于BaMg(CO ₃ ) ₂和BaMn(CO ₃ ) ₂。使用合成 BaFe(CO ₃ ) ₂粉末作为起始材料，与作为助熔剂介质的水相比，在含 CO ₂溶液存在下的反应表明 BaFe(CO ₃ ) ₂在高 PT 条件下不稳定。使用单晶 X 射线衍射 (XRD)、拉曼光谱和电子探针 (EP) 分析获得双碳酸盐的晶体结构和组成。鉴定出两种不同类型的新双碳酸盐： 实验衍生相属于与$\mathrm{电阻}\overline{3}米$ 和 $\mathrm{电阻}\overline{3}C$空间群，分别。拉曼光谱表明差异是由平行于 c 轴的超结构引起的。使用同步辐射的核前向散射确定新相中 Fe 的电荷和自旋状态。此外，估计了双碳酸盐在标准条件下的热力学性质，并构建了描述低温水性环境中稳定性场的相图，并将这些结果与天然水溶液进行了比较。