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Title: A new approach to approximate equation-of-motion coupled cluster with triple excitations

Accurate methods for excited, ionized, and electron-attached states are critical to the study of many chemical species such as reactive intermediates, radicals, and ionized systems. The equation-of-motion coupled cluster singles, doubles, and triples (EOM-CCSDT) family of methods is very accurate (roughly similar in accuracy as for CCSDT calculations of the ground state), but the computational cost scales iteratively as the eighth power of the system size. Many approximations already exist, although most either correct only the excited state or require an iterative $$\mathscr{O}$$(n 7) procedure which can also be prohibitively expensive. In this paper, new methods, termed EOM-CCSD(T)(a) and EOM-CCSD(T)(a)*, are proposed which correct both the ground and excited states based on a shared effective Hamiltonian, and the latter of which includes only non-iterative corrections to both the CCSD and EOM-CCSD energies. These methods are found to significantly improve the description of excited and ionized potential energy surfaces, equilibrium geometries, and harmonic frequencies; the accuracy is very close to that of full EOM-CCSDT.
Authors:
ORCiD logo [1] ;  [2]
  1. Univ. of Texas, Austin, TX (United States). Inst. for Computational Engineering and Sciences
  2. Univ. of Texas, Austin, TX (United States). Dept. of Chemistry
Publication Date:
Grant/Contract Number:
FG02-07ER15884
Type:
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 145; Journal Issue: 12; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Research Org:
Univ. of Texas, Austin, TX (United States). Inst. for Computational Engineering and Sciences
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1468931
Alternate Identifier(s):
OSTI ID: 1326117

Matthews, Devin A., and Stanton, John F.. A new approach to approximate equation-of-motion coupled cluster with triple excitations. United States: N. p., Web. doi:10.1063/1.4962910.
Matthews, Devin A., & Stanton, John F.. A new approach to approximate equation-of-motion coupled cluster with triple excitations. United States. doi:10.1063/1.4962910.
Matthews, Devin A., and Stanton, John F.. 2016. "A new approach to approximate equation-of-motion coupled cluster with triple excitations". United States. doi:10.1063/1.4962910. https://www.osti.gov/servlets/purl/1468931.
@article{osti_1468931,
title = {A new approach to approximate equation-of-motion coupled cluster with triple excitations},
author = {Matthews, Devin A. and Stanton, John F.},
abstractNote = {Accurate methods for excited, ionized, and electron-attached states are critical to the study of many chemical species such as reactive intermediates, radicals, and ionized systems. The equation-of-motion coupled cluster singles, doubles, and triples (EOM-CCSDT) family of methods is very accurate (roughly similar in accuracy as for CCSDT calculations of the ground state), but the computational cost scales iteratively as the eighth power of the system size. Many approximations already exist, although most either correct only the excited state or require an iterative $\mathscr{O}$(n7) procedure which can also be prohibitively expensive. In this paper, new methods, termed EOM-CCSD(T)(a) and EOM-CCSD(T)(a)*, are proposed which correct both the ground and excited states based on a shared effective Hamiltonian, and the latter of which includes only non-iterative corrections to both the CCSD and EOM-CCSD energies. These methods are found to significantly improve the description of excited and ionized potential energy surfaces, equilibrium geometries, and harmonic frequencies; the accuracy is very close to that of full EOM-CCSDT.},
doi = {10.1063/1.4962910},
journal = {Journal of Chemical Physics},
number = 12,
volume = 145,
place = {United States},
year = {2016},
month = {9}
}