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Non-iterative fifth-order triple and quadruple excitation energy corrections in correlated methods

✍ Scribed by Rodney J. Bartlett; J.D. Watts; S.A. Kucharski; J. Noga

Book ID
103027482
Publisher
Elsevier Science
Year
1990
Tongue
English
Weight
718 KB
Volume
165
Category
Article
ISSN
0009-2614

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✦ Synopsis

In critical cases, single-reference correlated methods like coupled-cluster theory or its quadratic CI approximations fail because of the importance of additional highly excited excitations that cannot usually be included, like connected triple and quadruple excitations. Here we present the first, non-iterative method to evaluate the full set of fifth-order corrections to CCSD and QCISD and assess their accuracy compared to full CI for the very sensitive Be2 curve and other cases.

📜 SIMILAR VOLUMES

Iterative and non-iterative triple excit
Iterative and non-iterative triple excitation corrections in coupled-cluster methods for excited electronic states: the EOM-CCSDT-3 and EOM-CCSD(T̃) methods
✍ John D. Watts; Rodney J. Bartlett 📂 Article 📅 1996 🏛 Elsevier Science 🌐 English ⚖ 532 KB

New iterative and non-iterative triple excitation corrections to EOM-CCSD are presented based upon the CCSDT-3 method. This method is recommended formally, since it fully employs the EOM-CCSD Hamiltonian /t = exp[-(T 1 + T2)]H exp(T I + T z) in its development. This permits defining iterative EOM-CC