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{To the Editors of the Journal of Chemical Physics,}

\opening{Dear Editors,}

\justifying

Please find enclosed our manuscript entitled \textit{``Accurate full configuration interaction correlation energy estimates for five- and six-membered ring molecules''}, 
which we would like you to consider as a Regular Article in the \textit{Journal of Chemical Physics}.

Thanks to the selected configuration interaction (SCI) algorithm named \textit{Configuration Interaction using a Perturbative Selection made Iteratively} (CIPSI), in the present manuscript, we have been able to produce FCI-quality frozen-core correlation energies for twelve cyclic molecules in the correlation-consistent double-$\zeta$ Dunning basis set (cc-pVDZ).
These estimates, which are likely accurate to a few tenths of a millihartree, have been obtained by extrapolating \textit{orbital-optimized} CIPSI energies to the FCI limit. 
Compared to natural orbitals, we have shown that, by using energetically optimized orbitals, one can reduce the size of the variational space by one order of magnitude for the same variational energy.

Having at hand these reference FCI energies, we have been able to faithfully benchmark and study the convergence properties of three families of popular electronic structure methods: i) MP2, MP3, MP4, and MP5, ii) CC2, CC3, and CC4, and iii) CCSD, CCSDT, and CCSDTQ.
The performance of the ground-state gold standard CCSD(T) as well as the completely renormalized CC model, CR-CC(2,3), are also investigated.

Because of the novel theoretical developments described in this manuscript and the usefulness of benchmark sets and their corresponding reference data for the electronic structure community, we expect this work to be of interest to a wide audience within the chemistry and physics communities.

We suggest Cyrus Umrigar, Sandeep Sharma, Nicholas Mayhall, Janus Eriksen, Seiichiro Ten-no, and Piotr Piecuch as potential referees.

We look forward to hearing from you soon.

\closing{Sincerely,}


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