Title: A statistical perspective on microsolvation Show Chinese title

Title: 微溶剂化的统计观点

Abstract: The lack of a procedure to determine equilibrium thermodynamic properties of a small system interacting with a bath is frequently seen as a weakness of conventional statistical mechanics. A typical example for such a small system is a solute surrounded by an explicit solvation shell. One way to approach this problem is to enclose the small system of interest in a large bath of explicit solvent molecules, considerably larger than the system itself. The explicit inclusion of the solvent degrees of freedom is obviously limited by the available computational resources. A potential remedy to this problem is a microsolvation approach where only a few explicit solvent molecules are considered and surrounded by an implicit solvent bath. Still, the sampling of the solvent degrees of freedom is challenging with conventional grand canonical Monte Carlo methods, since no single chemical potential for the solvent molecules can be defined in the realm of small-system thermodynamics. In this work, a statistical thermodynamic model based on the grand canonical ensemble is proposed that avoids the conventional system size limitations and accurately characterizes the properties of the system of interest subject to the thermodynamic constraints of the bath. We extend an existing microsolvation approach to a generalized multi-bath "micro-statistical" model and show that the previously derived approaches result as a limit of our model. The framework described here is universal and we validate our method numerically for a Lennard-Jones model fluid. Show Chinese abstract

Abstract: 缺乏一种确定与浴相互作用的小系统平衡热力学性质的程序，通常被视为传统统计力学的弱点。 一个典型的这种小系统的例子是被显式溶剂化壳包围的溶质。 解决这个问题的一种方法是将感兴趣的小系统封装在一个比系统本身大得多的显式溶剂分子浴中。 显然，由于可用的计算资源有限，溶剂自由度的显式包含受到限制。 解决这个问题的一个潜在方法是微溶剂化方法，其中只考虑少量显式溶剂分子，并被隐式溶剂浴包围。 尽管如此，使用传统的巨正则蒙特卡罗方法对溶剂自由度进行采样仍然具有挑战性，因为在小系统热力学范围内无法为溶剂分子定义单一的化学势。 在本工作中，提出了一种基于巨正则系综的统计热力学模型，该模型避免了传统系统大小限制，并能准确表征受浴热力学约束的兴趣系统性质。 我们扩展了一个现有的微溶剂化方法，以适用于广义多浴“微统计”模型，并表明之前推导的方法是我们的模型的一个极限情况。 这里描述的框架是通用的，我们对一个Lennard-Jones模型流体数值验证了我们的方法。