使多体相互作用近似成对可加：极化多体展开方法
Making Many-Body Interactions Nearly Pairwise Additive: The Polarized Many-Body Expansion Approach
摘要：
多体展开法（MBE）是一种模拟凝聚相化学体系的有效工具，通常可以避免通常电子结构方法的计算成本。然而，它通常需要高于2体的条款，以实现定量的准确性。在这项工作中，我们提出了极化MBE（PolBE）的方法，每个MBE能量的贡献被视为一个嵌入问题。在每个能量项中，一个较小的片段被嵌入到一个较大的，极化的环境中，只有一个小区域被处理在高层次的理论使用嵌入式平均场论。极化环境的作用被认为是至关重要的，在2体水平上提供定量的准确性。PolBE准确地预测非共价相互作用能的一些系统，包括CO $_2$，水和水合离子簇，与各种相互作用机制，从弱分散到强静电在这项工作中考虑。我们进一步证明了PolBE相互作用能主要是成对的，不像通常的真空分子束外延，需要高阶项，以达到类似的精度。我们的数值计算表明，PolBE往往比其他广泛使用的嵌入式MBE方法，如静电嵌入式MBE更好地执行。由于缺乏昂贵的对角化的Fock矩阵和它的并行性质，PolBE是一个很有前途的方式来访问凝聚相系统的混合密度泛函，难以处理与目前可用的方法。
英文摘要：
The Many-Body Expansion (MBE) is a useful tool to simulate condensed phase chemical systems, often avoiding the steep computational cost of usual electronic structure methods. However, it often requires higher than 2-body terms to achieve quantitative accuracy. In this work, we propose the Polarized MBE (PolBE) method where each MBE energy contribution is treated as an embedding problem. In each energy term, a smaller fragment is embedded into a larger, polarized environment and only a small region is treated at the high-level of theory using embedded mean-field theory. The role of polarized environment was found to be crucial in providing quantitative accuracy at the 2-body level. PolBE accurately predicts non-covalent interaction energies for a number of systems, including CO$_2$, water, and hydrated ion clusters, with a variety of interaction mechanisms, from weak dispersion to strong electrostatics considered in this work. We further demonstrate that the PolBE interaction energy is predominantly pairwise unlike the usual vacuum MBE which requires higher-order terms to achieve similar accuracy. We numerically show that PolBE often performs better than other widely used embedded MBE methods such as the electrostatically embedded MBE. Owing to the lack of expensive diagonalization of Fock matrices and its embarrassingly parallel nature, PolBE is a promising way to access condensed phase systems with hybrid density functionals that are difficult to treat with currently available methods.
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