Fajen O Jonathan, Brorsen Kurt R
Department of Chemistry, University of Missouri, Columbia, Missouri 65203, USA.
J Chem Phys. 2021 Dec 21;155(23):234108. doi: 10.1063/5.0071423.
This study implements the full multicomponent third-order (MP3) and fourth-order (MP4) many-body perturbation theory methods for the first time. Previous multicomponent studies have only implemented a subset of the full contributions, and the present implementation is the first multicomponent many-body method to include any connected triples contribution to the electron-proton correlation energy. The multicomponent MP3 method is shown to be comparable in accuracy to the multicomponent coupled-cluster doubles method for the calculation of proton affinities, while the multicomponent MP4 method is of similar accuracy as the multicomponent coupled-cluster singles and doubles method. From the results in this study, it is hypothesized that the relative accuracy of multicomponent methods is more similar to their single-component counterparts than previously assumed. It is demonstrated that for multicomponent MP4, the fourth-order triple-excitation contributions can be split into electron-electron and electron-proton contributions and the electron-electron contributions ignored with very little loss of accuracy of protonic properties.
本研究首次实现了全多组分三阶（MP3）和四阶（MP4）多体微扰理论方法。以往的多组分研究仅实现了全贡献的一个子集，而目前的实现是首个包含对电子-质子关联能的任何连接三重态贡献的多组分多体方法。结果表明，在计算质子亲和能时，多组分MP3方法的精度与多组分耦合簇双激发方法相当，而多组分MP4方法的精度与多组分耦合簇单激发和双激发方法相似。根据本研究的结果，推测多组分方法的相对精度与其单组分对应方法比之前假设的更为相似。结果表明，对于多组分MP4，四阶三重激发贡献可分为电子-电子贡献和电子-质子贡献，忽略电子-电子贡献对质子性质的精度损失很小。
