Thermodynamics of droplets under extreme ambient conditions by molecular simulation

流体的热力学性质在极端环境条件下液滴动力学的研究和描述中起着核心作用。与现象学模型相比，分子模型和模拟具有良好的物理基础，因此非常适合在极端条件下预测这些性质。在第一期资助期内，建立了相关物质的分子力场模型，研究了平衡条件下的流体界面性质，蒸发过程中的非平衡过程是本项目阶段的重点。因此，对依赖于温度、压力和化学势驱动梯度的传质进行了采样，并与经典输运模型进行了比较。利用大质量平行分子动力学模拟了平面和强弯曲界面上的蒸发过程。极端条件，即接近临界，是特别感兴趣的。模拟将在固定、准固定和固定边界条件下进行，这将根据具体情况确定方法的优缺点。除了纯真实流体的蒸发，如氧气、丙酮和水，它们的混合物也将被研究。此外，模型系统将被认为可以定义为严格满足经典输运模型中通常提出的“理想性”假设。

The thermodynamic properties of fluids play a central role in the investigation and description of droplet dynamics under extreme ambient conditions. In contrast to phenomenological models, molecular modeling and simulation has a sound physical basis and is therefore well suited for predictions of such properties under extreme conditions. After setting up molecular force field models for the relevant substances and studying their fluid interface properties under equilibrium conditions in the first funding period, non-equilibrium processes during evaporation are in the focus of this project phase. Thereby, mass transfer depending on driving gradients of temperature, pressure and chemical potential are sampled and compared to classical transport models. Evaporation processes across planar as well as strongly curved interfaces are simulated by massively-parallel molecular dynamics. Extreme conditions, i.e. being close to criticality, are of particular interest. The simulations will be carried out under stationary, quasi-stationary and instationary boundary conditions, which will allow for the identification of methodological advantages and disadvantages, depending on the scenario. Next to the evaporation of pure real fluids, such as oxygen, acetone and water, also their mixtures will be studied. Moreover, model systems will be considered that can be defined such that assumptions on "ideality", commonly made in classical transport models, are strictly fulfilled.