Chair for Theoretical Chemistry and Catalysis Research Center, Technische Universität München, Lichtenbergstrasse 4, D-85747 Garching, Germany.
Department of Physics and Astronomy, University College London, London WC1E 6BT, U.K.
J Chem Theory Comput. 2020 Sep 8;16(9):5723-5735. doi: 10.1021/acs.jctc.0c00151. Epub 2020 Aug 7.
The treatment of electrostatic interactions is a key ingredient in the force field-based simulation of condensed phase systems. Most approaches used fixed, site-specific point charges. Yet, it is now clear that many applications of force fields (FFs) demand more sophisticated treatments, prompting the implementation of charge equilibration methods in polarizable FFs to allow the redistribution of charge within the system. One approach allowing both, charge redistribution and site-specific polarization, while at the same time solving methodological shortcomings of earlier methods, is the first-principles-derived atom-condensed Kohn-Sham density functional theory method approximated to the second order (ACKS2). In this work, we present two fragment approaches to ACKS2, termed f-ACKS2 and a self-consistent version, scf-ACKS2, that treat condensed phase systems as a collection of electronically polarizable molecular fragments. The fragmentation approach to ACKS2 not only leads to a more transferable and less system-specific collection of electronic response parameters but also opens up the method to large condensed phase systems. We validate the accuracies of f-ACKS2 and scf-ACKS2 by comparing polarization energies and induced dipole moments for a number of charged hydrocarbon dimers against DFT reference calculations. Finally, we also apply both fragmented ACKS2 variants to calculate the polarization energy for electron-hole pair separation along a chain of anthracene molecules and find excellent agreement with reference DFT calculations.
静电相互作用的处理是基于力场的凝聚相系统模拟的关键组成部分。大多数方法使用固定的、特定位置的点电荷。然而，现在很明显，力场（FFs）的许多应用需要更复杂的处理方法，这促使在极化 FFs 中实现电荷平衡方法，以允许在系统内重新分配电荷。一种允许电荷再分配和特定位置极化的方法，同时解决了早期方法的方法学缺点，是基于第一性原理的原子凝聚 Kohn-Sham 密度泛函理论方法（ACKS2）的近似方法。在这项工作中，我们提出了两种用于 ACKS2 的片段方法，分别称为 f-ACKS2 和自洽版本 scf-ACKS2，它们将凝聚相系统视为一组电子极化的分子片段。ACKS2 的片段化方法不仅导致更可转移和更少系统特异性的电子响应参数集合，而且还为大型凝聚相系统开放了该方法。我们通过比较一系列带电烃类二聚体的极化能和诱导偶极矩与 DFT 参考计算，验证了 f-ACKS2 和 scf-ACKS2 的准确性。最后，我们还应用这两种片段化的 ACKS2 变体来计算沿蒽分子链的电子-空穴对分离的极化能，并与参考 DFT 计算结果非常吻合。
