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arXiv · 2509.14157

Frozen Natural Orbitals based Equation-of-motion coupled-cluster singles, doubles and triples for Ionized, Double-Ionized, Electron Attached and Two-Electron Attached states

Manisha·Prashant Uday Manohar
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Abstract

In this work, we present frozen natural orbital (FNO) based implementations of equation-of-motion (EOM) coupled-cluster (CC) with singles, doubles, and triples (SDT) for ionization potential (IP), double ionization potential (DIP), electron attachment (EA), and double electron attachment (DEA) variants. For EOM-CC with singles and doubles (SD), the FNO approach has already been studied by Krylov and co-workers for IP variant and for spin-flipping and spin-conserving excited states (respectively, the SF and EE variants) for both total energies and energy-gaps. Recently, we presented FNO-CCSDT performance for ground state energies of molecules, triplet-singlet gaps and for numerical estimation force constants of some diatomic molecules. Now we present our study on performance of IP, DIP, EA and DEA variants of FNO-EOM-CCSDT in computing total-energies, and for target-reference and target-target energy-gaps. Following earlier studies by us and by Krylov and co-workers, we also present the XFNO-EOM-CCSDT approach for these variants and examine its performance for total energies and energy-gaps.

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Manisha, Prashant Uday Manohar. 2025-09-17. Frozen Natural Orbitals based Equation-of-motion coupled-cluster singles, doubles and triples for Ionized, Double-Ionized, Electron Attached and Two-Electron Attached states. https://arxiv.org/abs/2509.14157

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