Intra- versus intermolecular forces: the influence of solute-solvent interactions on the structure and properties of extended molecules

与气相相比，溶剂环境对扩展分子的几何和电子结构有显著影响。由于在绝大多数情况下，化学过程的研究是在液相中进行的，因此，关于溶质-溶剂相互作用影响的知识对于化学结构和性质的解释和预测至关重要。然而，为此目的应用理论方法构成了一项极具挑战性的任务，因为溶质-溶剂系统只能通过对系统的复杂构象景观进行完全采样来适当描述。本项目的目的是结合经典分子动力学（MD）力场方法和量子化学方法来描述分子与溶剂分子之间的相互作用，并量化系统中分子间和分子内的相互作用，以定义各种溶剂环境诱导的扩展分子的结构变化。MD模拟将用于扫描系统的构象空间，然后MD淬火将用于提取一组结构（分子加上溶剂分子的壳），然后可以用精确的量子化学方法进一步研究。对于后者，我们将采用我们最近开发的增量分子碎片方案，该方案可用于将分子的总能量分解为键能和非键能贡献。通过对后者使用适应对称的分子间摄动理论（SAPT）方法，溶质-溶剂系统中的相互作用可以用单个相互作用能量项来表征，如静电和色散相互作用。因此，将扩展溶解分子的分子内相互作用与气相相互作用进行比较，可以深入了解分子内弥散相互作用对外部环境的依赖性。

The geometric and electronic structure of extended molecules can be significantly influenced by a solvent environment when compared with the gas phase. Since, in the vast majority of cases, the study of chemical processes takes place in the liquid phase, the knowledge about the impact of the solute-solvent interactions therefore are crucial for the interpretation and prediction of chemical structures and properties. The application of theoretical methods for this purpose, however, constitutes a highly challenging task, because the solute-solvent system can only be properly described by completely sampling the complex conformational landscape of the system. The aim of this project is to employ a combination of classical molecular dynamics (MD) force field methods and quantum chemistry methods for describing the interactions between a molecule with solvent molecules and to quantify both inter- and intramolecular interactions in the system in order to define structural changes of extended molecules induced by various solvent environments. The MD simulations will be done in order to scan the conformational space of the system, and MD quenching will then be used for extracting a set of structures (molecule plus shell of solvent molecules) which can then be studied further with accurate quantum chemistry methods. For the latter, our recently developed incremental molecular fragmentation scheme will be employed which can be used to decompose the total energy of a molecule into bonded and nonbonded energy contributions. By using symmetry-adapted intermolecular perturbation theory (SAPT) methods for the latter, the interactions in the solute-solvent system can then be characterised by individual interaction energy terms, like electrostatic and dispersion interactions. With this, a comparison between intramolecular interactions of extended dissolved molecules to the interactions in the gas phase can thus give an insight in the dependence of intramolecular dispersion interactions on the outer environment.