Fragment-Based Restricted Active Space Configuration Interaction with Second-order corrections Embedded in Periodic Hartree-Fock Wavefunction
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We present a computational scheme for restricted-active-space configuration inter- action (RASCI) calculations combined with second-order perturbation theory (RASCI- PT2) on a fragment of a periodic system embedded in the periodic Hartree-Fock (HF) wavefunction. This method allows one to calculate the electronic structure of localized strongly-correlated features in crystals and surfaces. The scheme was implemented via an interface between the Cryscor and Q-Chem codes. To evaluate the performance of the embedding method, we explored dissociation of fluorine atom from a lithium flu- oride surface and partially fluorinated graphane layer. The results show that RASCI and RASCI-PT2 embedded in periodic HF are able to produce well-behaved potential energy surfaces and accurate dissociation energies.