Nonadditivity in Molecular Interactions

在这个理论与计算化学的项目中， 化学系的性质 在各种系统中能量的不可加性 用量子力学的方法来探索。 超分子 方法和微扰理论正在 就业。 各种类型的系统正在 研究，包括非极性系统，极性系统，和混合 极性-非极性系统（如稀有气体-水聚集体）。 得到的解析势明确地包括 多体效应，因此适用于模拟 凝聚相和团簇的行为。 %%% 非常大的分子和固体的能量通常 假设可以很好地近似为 组成系统的小分子，甚至原子。 在这个项目中，理论方法被用来评估 这些假设的准确性，并制定更准确的 大系统的能量。

In this project in the Theoretical and Computational Chemistry program of the Division of Chemistry the nature of nonadditivity of energies in a variety of systems is being explored by quantum mechanical methods. Both the supermolecule method and symmetry-adapted perturbation theory are being employed. A wide variety of types of systems are being studied, including nonpolar systems, polar systems, and mixed polar-nonpolar systems (such as rare gas - water aggregates). Analytic potentials are being obtained which explicitly include multibody effects and which are thus suitable for simulations of the behavior of both condensed phases and clusters. %%% The energies of very large molecules and solids are often assumed to be approximated well by the sum of the energies of the smaller molecules, or even the atoms, making up the system. In this project theoretical methods are being used to assess the accuracy of such assumptions and to develop more accurate energies of large systems.