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FragPT2: Multifragment Wave Function Embedding with Perturbative Interactions
DOI:10.1021/acs.jctc.4c01221.png)
Abstract
En 中文
Embedding techniques allow the efficient description of correlations within localized fragments of large molecular systems while accounting for their environment at a lower level of theory. We introduce FragPT2: a novel embedding framework that addresses multiple interacting active fragments. Fragments are assigned separate active spaces, constructed by localizing canonical molecular orbitals. Each fragment is then solved with a multireference method, self-consistently embedded in the mean field from other fragments. Finally, interfragment correlations are reintroduced through multireference perturbation theory. Our framework provides an exhaustive classification of interfragment interaction terms, offering a tool to analyze the relative importance of various processes such as dispersion, charge transfer, and spin exchange. We benchmark FragPT2 on challenging test systems, including N2 dimers, multiple aromatic dimers, and butadiene. We demonstrate that our method can be successful even for fragments defined by cutting through a covalent bond.
Keywords:
SELF-CONSISTENT-FIELD
ELECTRON CORRELATION
QUANTUM
IMPLEMENTATION
MODELS
CASSCF
STATES
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