Exploiting Non-Abelian\nPoint-Group Symmetry to Estimate\nthe Exact Ground-State Correlation Energy of Benzene in a Polarized\nSplit-Valence Triple-Zeta Basis Set

Local electronic-structure methods in quantum chemistry\noperate\non the ability to compress electron correlations more efficiently\nin\na basis of spatially localized molecular orbitals than in a parent\nset of canonical orbitals. However, many typical choices of localized\norbitals tend to be related by selected, near-exact symmetry operations\nwhenever a molecule belongs to a point group, a feature which remains\nlargely unexploited in most local correlation methods. The present\nLetter demonstrates how to leverage a recent unitary protocol for\nenforcing symmetry properties among localized orbitals to yield a\nhigh-accuracy estimate of the exact ground-state correlation energy\nof benzene (<i>D</i><sub>6<i>h</i></sub>) in correlation-consistent\npolarized basis sets of both double- and triple-ζ quality. Through\nan initial application to many-body expanded full configuration interaction\n(MBE-FCI) theory, we show how molecular point-group symmetry can lead\nto computational savings that are inversely proportional to the order\nof the point group in a manner generally applicable to the acceleration\nof modern local correlation methods.