What is the largest system (organic molecule) which total energy was calculated by full configuration interaction? Lets say with DZV or similar basis set. How far can we get with CI in larger basis sets?

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    $\begingroup$ Lets do a competition: He-dimer He$_2$, Basis: [11s]4p3d1f+1p2d1f. (1995) dx.doi.org/10.1063/1.469060 , $\endgroup$ Jun 8, 2017 at 17:45
  • $\begingroup$ Another hint: "deterministic FCI calculations for 6e^- have not exceeded the level of TZ basis sets" dx.doi.org/10.15278/isms.2016.TK07 (2016). While they themselves do Li$_2$ with a cbs extrapolation from AUG-CC-PCV5Z and AUG-CC-PCV6Z. $\endgroup$ Jun 8, 2017 at 17:51
  • $\begingroup$ related: mattermodeling.stackexchange.com/q/9495/5 $\endgroup$ Aug 9, 2022 at 5:53

2 Answers 2


FCI of N2 with about 10^10 CSFs must be the largest such calculation...

Ref: A full-configuration benchmark for the N2 molecule, Elda Rossi, Gian Luigi Bendazzoli, Stefano Evangelisti, Daniel Maynau, https://doi.org/10.1016/S0009-2614(99)00791-5


J. Chem. Phys. 125, 124311 (2006) reports full configuration interaction (FCI) calculations on BN, BP, AlN, and AlP in the cc-pVTZ basis set:

The full CI calculations consisted of about 45x10^9 determinants for the singlets and about 35x10^9 determinants for the triplets.

J. Chem. Phys. 147, 184111 (2017) reports FCI calculations for the chromium trimer with a (20e,20o) active space and for pentacene with a (22e,22o) active space. They also did a single CI iteration (they did not converge the FCI calculation!) with an active space of (24e,24o) for the chromium tetramer with 914 058 513 424 determinants.


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