标题： 硅酸盐-水混合物在行星条件下的线性混合近似 显示英文标题

标题： The linear-mixing approximation in silica-water mixtures at planetary conditions

摘要： 线性混合近似（LMA）常用于行星模型中，以计算混合物的状态方程（EoSs）。一种常见的假设行星成分是岩石和水的混合物。在此，我们评估LMA在天王星和海王星内部相关的压力-温度条件下的准确性。我们使用第一性原理模拟进行分子动力学（MD）模拟，并考虑3000 K温度下纯水、纯二氧化硅以及1:1和1:4比例的二氧化硅-水分子分数，在30到600 GPa的压力范围内。我们发现，在约150-600 GPa范围内，LMA的误差在几个百分比以内（<~5%），其中推导密度的差异符号取决于混合物的具体组成。我们还表明，对于1:4比例的二氧化硅-水混合物，岩石的存在会使超离子水的转变延迟约70 GPa。最后，我们注意到电子理论（泛函）的选择会影响状态方程，并在密度上引入约10%的不确定性。我们的研究展示了行星条件下相图的复杂性，以及对岩石-水混合物及其对推导行星成分影响更好理解的必要性。 显示英文摘要

摘要： The Linear Mixing Approximation (LMA) is often used in planetary models for calculating the equations of state (EoSs) of mixtures. A commonly assumed planetary composition is a mixture of rock and water. Here we assess the accuracy of the LMA for pressure-temperature conditions relevant to the interiors of Uranus and Neptune. We perform MD simulations using ab-initio simulations and consider pure-water, pure-silica, and 1:1 and 1:4 silica-water molecular fractions at temperature of 3000 K and pressures between 30 and 600 GPa. We find that the LMA is valid within a few percent (<~5%) between ~150-600 Gpa, where the sign of the difference in inferred density depends on the specific composition of the mixture. We also show that the presence of rocks delays the transition to superionic water by ~70 GPa for the 1:4 silica-water mixture. Finally, we note that the choice of electronic theory (functionals) affect the EoS and introduces an uncertainty in of the order of 10% in density. Our study demonstrates the complexity of phase diagrams in planetary conditions and the need for a better understanding of rock-water mixtures and their effect on the inferred planetary composition.