Abstract Ab initio molecular dynamics simulations were performed at pressures and temperatures up to 160 GPa and 4000 K, in order to obtain equations of state (EOS) for CO and CO2 fluids. We found that polymerisation of CO and CO2 fluids starts at low pressures, and that including the effect of polymerisation is essential for accurate EOS. EOSs for CO and CO2 determined from methods using experimental data, or classical potentials that ignore the changes in speciation, should be treated with caution when extrapolated beyond the examined pressures and temperatures. The obtained data was fitted to a modified Lee and Kesler EOS for both CO and CO2 fluids. The thermodynamic calculations for the decarbonation reactions of both MgCO3 and CaCO3 using the derived CO2 EOS reproduced the experimental data and theoretical calculations at low pressures. Both MgCO3 and CaCO3 pure phases are found to be stable in the upper mantle compared to CO2. However, they both become destabilised when approaching lower mantle conditions.

中文翻译：

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CO和CO2流体的状态方程及其在高压高温脱碳反应中的应用

摘要 为了获得 CO 和 CO2 流体的状态方程 (EOS)，在高达 160 GPa 和 4000 K 的压力和温度下进行了从头算分子动力学模拟。我们发现 CO 和 CO2 流体的聚合在低压下开始，包括聚合的影响对于准确的 EOS 至关重要。使用实验数据的方法确定的 CO 和 CO2 的 EOS，或忽略形态变化的经典势，在外推超出检查的压力和温度时应谨慎处理。将获得的数据拟合到改进的 Lee 和 Kesler EOS 中的 CO 和 CO2 流体。使用衍生的 CO2 EOS 对 MgCO3 和 CaCO3 的脱碳反应的热力学计算再现了低压下的实验数据和理论计算。与 CO2 相比，MgCO3 和 CaCO3 纯相在上地幔中都是稳定的。然而，当接近下地幔条件时，它们都会变得不稳定。