Abstract We present a theoretical investigation, within the density functional theory and the quasi-harmonic approximation framework, on the stability properties of calcium carbonate (CaCO3) at the thermodynamic conditions of the Earth's lower mantle. We initially explored the structural properties of a low-pressure phase (aragonite) using three different approximations for the exchange-correlation potential, and find that all properties are better described, when compared to recent experimental data, by using the one that takes into account the van der Waals interactions. We used this approximation to compute the free energy of this mineral in several crystalline phases, and explored the respective thermodynamic properties at high temperatures and high pressures. The results on phase stability, thermal expansivity, specific heat, bulk modulus, and mass density were compared to available experimental data. Then, we built the phase diagram for this mineral and discussed its impact on the Earth's mantle properties.

中文翻译：

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高压高温下的碳酸钙：第一性原理研究

摘要 我们在密度泛函理论和准谐波近似框架内，对地球下地幔热力学条件下碳酸钙 (CaCO3) 的稳定性特性进行了理论研究。我们最初使用三种不同的交换相关势近似值探索了低压相（文石）的结构特性，并发现与最近的实验数据相比，所有特性都得到了更好的描述。范德瓦尔斯相互作用。我们使用这种近似来计算这种矿物在几个晶相中的自由能，并探索了高温高压下各自的热力学性质。相稳定性、热膨胀率、比热、体积模量、和质量密度与可用的实验数据进行了比较。然后，我们为这种矿物建立了相图，并讨论了它对地球地幔特性的影响。