Ab initio simulations for thermophysical properties of molecular HCNO mixtures

我们将计算各种HCNO化合物在海王星类行星内部典型的极端压力和温度条件下的热力学和传输特性。与子项目1和2类似，我们将采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。主要目标是生成水、氨、甲烷及其混合物的状态方程。这包括在热力学势和熵的计算方面的热力学数据的分析参数化。将研究流体中离解和电离过程的发生以及固相和超离子相的形成。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进行的。此外，我们还计算了HCNO混合物的扩散系数、粘度和导热系数。特别是富含氢的化学计量，代表在GPa压力范围内的行星热边界层的化学成分将进行研究。这里采用的从头算方法允许在部分解离和电离物质的这种运输过程的系统调查和表征。研究结果将用于在分项目5中为类海王星行星开发新的演化和层形成模型。

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.