Virtual orbital many-body expansions: A possible route towards the full configuration interaction limit

Abstract

In the present letter, it is demonstrated how full configuration interaction (FCI) results in extended basis sets may be obtained to within sub-kJ/mol accuracy by decomposing the energy in terms of many-body expansions in the virtual orbitals of the molecular system at hand. This extension of the FCI application range lends itself to two unique features of the current approach, namely that the total energy calculation can be performed entirely within considerably reduced orbital subspaces and may be so by means of embarrassingly parallel programming. Facilitated by a rigorous and methodical screening protocol and further aided by expansion points different from the Hartree-Fock solution, all-electron numerical results are reported for H${}_2$O in polarized core-valence basis sets ranging from double-$\zeta$ (10 $e$, 28 $o$) to quadruple-$\zeta$ (10 $e$, 144 $o$) quality.

20 pages, 3 figures, 1 table. * With respect to the original arXiv version (v1), the present version of the letter contains updated results. The original TZ and QZ values were unfortunately in error due to a subtle PySCF bug, which has since then been fixed

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• Cluster decomposition of full configuration interaction wave functions: a tool for chemical interpretation of systems with strong correlation
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