Grand-Canonical-like adaptive resolution of molecules with electrons

该项目旨在融合我们两个小组的专业知识，并在柏林的自适应分辨率模拟技术(ADRESS代码)和帕德伯恩的恒定化学势从头计算技术(ls++代码)之间建立一个接口。由此产生的代码将允许我们模拟一个量子经典大正则分子系统，其中分子可以根据它们瞬时所在的区域将分辨率从量子更改为经典，反之亦然。与标准开放边界QM/MM相比，该方法的优点在于，所得到的方法将严格基于开放系统概念上已确立的物理原理。与QM/MM相反，经验输入是最小的，只要不违反开放系统的原则，模拟结果就会具有物理一致性，而不需要通过更大的全量子计算进行系统的后验证。然后，我们将把新的程序应用于一个相关的物理化学问题，即计算苯丙氨酸在金属铂(111)表面上的吸附自由能。对于这样一个系统，在靠近地表的地方，人们需要电子自由度来检测水化和吸附之间的相互作用，而不是在远离表面的地方，水只起到热力学浴池的作用，因此可以经典地甚至在粗粒度水平上处理，因此我们的新方法为有效地研究这种系统提供了一个强有力的工具。

This project aims at merging the expertise of our two groups and build an interface between the adaptive resolution simulation technique of Berlin (AdResS code) with the constant chemical potential ab initio technique of Paderborn (ls++ code). The resulting code will allow us to simulate a quantum classical Grand Canonical molecular systems where molecules can change resolution from quantum to classical and vice versa according to the region where they are instantaneously located. The advantage, compared to standard open boundary QM/MM, is that the resulting method will be strictly based on conceptually well established physical principles of open systems. Contrary to QM/MM, the empirical input is minimal and as long as the principles of open systems are not violated, the simulation results will have physical consistency without the systematic need of post validation by larger full quantum calculations. We will then apply the new code to a relevant problem of physical chemistry, namely the calculation of the free energy of adsorption of phenylalanine on a metal, Pt(111) surface. For such a system, close to the surface, one needs electronic degrees of freedom to detect the interplay between hydration and adsorption, instead away from the surface water plays simply the role of a thermodynamic bath and thus can be treated classically or even at coarse-grained level, thus our new methodology represents a powerful tool for an efficient study of such systems.