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I recently found that PySCF supports coupled cluster calculations for periodic systems (link to the documentation: https://pyscf.org/user/pbc/mix_mol.html). That seems pretty unique: of course DFT in periodic systems is widely used (VASP, QuantimEspresso etc) but this is probably the first time I’ve seen any post-Harteee Fock method in a periodic system.

How does it work? In particular, what happens with the pseudopotentials, and what happens with the k-points? Are there any papers that describe either the general theory or the PySCF implementation?

Does any other software support this?

Can periodic CCSD(T)/CBS be considered a gold standard method in periodic systems the same way it is in non-periodic? (I’m thinking mainly of molecular crystals)

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    $\begingroup$ I just came across this article (DOI: 10.3389/fmats.2019.00123) through this answer: mattermodeling.stackexchange.com/a/9030/7606 . Perhaps this will help? $\endgroup$ Dec 19, 2023 at 5:31
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    $\begingroup$ The documentation you listed suggests that the k-points and pseudopotentials are handled incore at the Hartree–Fock level: given all the HF two-electron integrals (in PBC or not) stored in the eri object, one can compute coupled-cluster correction directly from them. Of course, that only answers your first question. $\endgroup$
    – elutionary
    Dec 27, 2023 at 20:20

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