Abstract A novel structure of calcium orthocarbonate Ca2CO4-Pnma has been discovered using ab-initio crystal structure prediction methods (AIRSS and USPEX) based on the density functional theory. This phase appears above 13 GPa and remains stable to at least 50 GPa and 2000 K according to the calculations within quasi-harmonic approximation. Thus, the discovered phase can be stable at Earth's transition zone and lower mantle P-T conditions. The carbon atoms in the discovered phase are presented in 4-fold coordination, and its structure is similar to the high-pressure and high-temperature α'H-Ca2SiO4 phase.

中文翻译：

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原碳酸钙，Ca2CO4-Pnma：在过渡带和下地幔中俯冲碳的潜在宿主

摘要 使用基于密度泛函理论的 ab-initio 晶体结构预测方法（AIRSS 和 USPEX）发现了一种新的原碳酸钙 Ca2CO4-Pnma 结构。根据准谐波近似内的计算，该相出现在 13 GPa 以上并在至少 50 GPa 和 2000 K 保持稳定。因此，发现的相可以在地球过渡带和下地幔 PT 条件下保持稳定。发现相中的碳原子以4重配位形式存在，其结构类似于高压高温α'H-Ca2SiO4相。