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12:11
Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
Published on: April 8, 2020
Implementation of the multireference Brillouin-Wigner and Mukherjee's coupled cluster methods with non-iterative
Kiran Bhaskaran-Nair1, Jiří Brabec, Edoardo Aprà
1William R. Wiley Environmental Molecular Sciences Laboratory, Battelle, Pacific Northwest National Laboratory, K8-91, P.O. Box 999, Richland, Washington 99352, USA.
The Journal of Chemical Physics
|September 11, 2012
Summary
State-specific multireference coupled cluster (SS-MRCC) methods, including triples, show strong performance. These non-iterative approaches accurately model electronic structures for various molecules, offering computational efficiency.
Area of Science:
- Quantum Chemistry
- Computational Chemistry
- Theoretical Chemistry
Background:
- Multireference coupled cluster (MRCC) methods are essential for describing systems with strong electron correlation.
- Accurate modeling of electronic structures requires accounting for electron excitations, particularly triples.
Purpose of the Study:
- To evaluate the performance of non-iterative state-specific multireference coupled cluster (SS-MRCC) methods.
- To assess the impact of triply excited cluster amplitudes on MRCC model accuracy.
- To compare SS-MRCC methods with traditional single-reference coupled cluster approaches.
Main Methods:
- Implementation and testing of Brillouin-Wigner (BW) and Mukherjee's (Mk) MRCC models with non-iterative triples (SS-MRCCSD(T)).
- Comparison with exact full configuration interaction (FCI) results for small molecules (H2O, N2, Be3).
- Benchmarking against single-reference coupled cluster methods for larger systems (naphthyne isomers).
Main Results:
- Non-iterative SS-MRCC methods, including triples, demonstrate good performance.
- Accurate results were obtained for small systems when compared to FCI.
- SS-MRCCSD(T) methods show competitive accuracy compared to single-reference coupled cluster methods for larger systems.
- The parallel performance of non-iterative implementations was analyzed.
Conclusions:
- Non-iterative SS-MRCC methods provide a computationally efficient and accurate approach for electronic structure calculations.
- These methods effectively incorporate the effects of triple excitations.
- The findings support the use of SS-MRCC methods for complex chemical systems.
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