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Main Authors: Gunasekera, Alexander, Lee, Nicholas, Tew, David P.
Format: Preprint
Published: 2024
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Online Access:https://arxiv.org/abs/2403.05389
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author Gunasekera, Alexander
Lee, Nicholas
Tew, David P.
author_facet Gunasekera, Alexander
Lee, Nicholas
Tew, David P.
contents Properly spin-adapted coupled-cluster theory for general open-shell configurations remains an active area of research in electronic structure theory. In this contribution we examine Lindgren's normal-ordered exponential ansatz to correlate specific spin states using spin-free excitation operators, with the aid of automatic equation generation software. We present an intermediately normalised and size-extensive reformulation of the unlinked working equations, and analyse the performance of the method with single and double excitations for simple molecular systems in terms of accuracy and size-consistency.
format Preprint
id arxiv_https___arxiv_org_abs_2403_05389
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Multi-reference coupled cluster theory using the normal ordered exponential ansatz
Gunasekera, Alexander
Lee, Nicholas
Tew, David P.
Chemical Physics
Properly spin-adapted coupled-cluster theory for general open-shell configurations remains an active area of research in electronic structure theory. In this contribution we examine Lindgren's normal-ordered exponential ansatz to correlate specific spin states using spin-free excitation operators, with the aid of automatic equation generation software. We present an intermediately normalised and size-extensive reformulation of the unlinked working equations, and analyse the performance of the method with single and double excitations for simple molecular systems in terms of accuracy and size-consistency.
title Multi-reference coupled cluster theory using the normal ordered exponential ansatz
topic Chemical Physics
url https://arxiv.org/abs/2403.05389