Ab initio simulations for thermophysical properties of molecular HCNO mixtures

我们将计算在海王星类行星内部典型的压力和温度极端条件下各种HCNO化合物的热力学和输运性质。与子项目1和子项目2类似，我们将使用基于密度泛函理论和分子动力学的多粒子物理学中最先进的从头算方法。一个主要目标是生成水、氨、甲烷及其混合物的状态方程。这包括热力学数据的热力学势的解析参数化和熵的计算。将研究流体中离解和电离过程的发生，以及固体和上离子相的形成。这里计算的状态方程将直接用于行星内部的建模，这是在其他子项目中执行的。我们的结果还将与子项目9的实验结果进行比较。此外，我们还将计算HCNO混合物的扩散系数、粘度和热导率。特别是，将研究在GPA压力范围内代表地球热边界层化学成分的富氢化学计量学。这里使用的从头算方法允许对部分解离和电离物质中的这种传输过程进行系统的研究和表征。这些结果将用于子项目5中开发类海王星行星的新演化和层形成模型。

We will calculate thermodynamic and transport properties of various HCNO compounds under extreme conditions of pressure and temperature typical for the interior of Neptune-like planets. Similar as in subprojects 1 and 2, we will employ state-of-the-art ab initio methods from many-particle physics that are based on density functional theory and molecular dynamics. A primary goal is the generation of equations of state for water, ammonia, methane, and their mixtures. This includes the analytic parametrization of the thermodynamic data in terms of thermodynamic potentials and the calculation of the entropy. The occurrence of dissociation and ionization processes in the fluid as well as the formation of solid and superionic phases will be investigated. The equations of state calculated here will be directly employed in the modeling of planetary interiors, which is performed in other subprojects. Our results will also be compared with the experimental findings from subproject 9.Moreover, we will calculate the diffusion coefficients, viscosities, and thermal conductivities of the HCNO mixtures. Especially hydrogen-rich stoichiometries that represent the chemical composition in thermal boundary layers in the planet at the GPa pressure range will be investigated. The ab initio methods employed here allow for a systematic investigation and characterization of such transport processes in partially dissociated and ionized matter. The results will be used in the development of novel evolution and layer formation models for Neptune-like planets in subproject 5.