Journal
JOURNAL OF CHEMICAL PHYSICS
Volume 141, Issue 16, Pages -Publisher
AMER INST PHYSICS
DOI: 10.1063/1.4898709
Keywords
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Funding
- U.S. National Science Foundation (NSF) [CHE-1265945, DGE-1256082]
- (U.S.) Department of Energy (DOE) [DE-SC0006863]
- Gaussian, Inc.
- University of Washington Student Technology and Royalty Research Fund
- Direct For Mathematical & Physical Scien
- Division Of Chemistry [1265945] Funding Source: National Science Foundation
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Methods for fast and reliable computation of electronic excitation energies are in short supply, and little is known about their systematic performance. This work reports a comparison of several low-scaling approximations to the equation of motion coupled cluster singles and doubles (EOM-CCSD) and linear-response coupled cluster singles and doubles (LR-CCSD) equations with other single reference methods for computing the vertical electronic transition energies of 11 small organic molecules. The methods, including second order equation-of-motion many-body perturbation theory (EOM-MBPT2) and its partitioned variant, are compared to several valence and Rydberg singlet states. We find that the EOM-MBPT2 method was rarely more than a tenth of an eV from EOM-CCSD calculated energies, yet demonstrates a performance gain of nearly 30%. The partitioned equation-of-motion approach, P-EOM-MBPT2, which is an order of magnitude faster than EOM-CCSD, outperforms the CIS(D) and CC2 in the description of Rydberg states. CC2, on the other hand, excels at describing valence states where P-EOM-MBPT2 does not. The difference between the CC2 and P-EOM-MBPT2 can ultimately be traced back to how each method approximates EOM-CCSD and LR-CCSD. The results suggest that CC2 and P-EOM-MBPT2 are complementary: CC2 is best suited for the description of valence states while P-EOM-MBPT2 proves to be a superior O(N-5) method for the description of Rydberg states. (c) 2014 AIP Publishing LLC.
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