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12:11
Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
Published on: April 8, 2020
Explicitly correlated coupled-cluster singles and doubles method based on complete diagrammatic equations.
Toru Shiozaki1, Muneaki Kamiya, So Hirata
1Quantum Theory Project and The Center for Macromolecular Science and Engineering, Department of Chemistry and Department of Physics, University of Florida, Gainesville, Florida 32611-8435, USA.
The Journal of Chemical Physics
|December 3, 2008
Summary
New computer codes implement explicitly correlated coupled-cluster methods (CCSD-R12) with point-group symmetry. These benchmarks assess approximate CC-R12 methods, showing CCSD(R12) and CCSD(2)(R12) are highly accurate.
Area of Science:
- Quantum Chemistry
- Computational Chemistry
- Theoretical Chemistry
Background:
- Explicitly correlated coupled-cluster (CC) methods incorporate inter-electron distance, improving accuracy.
- Previous implementations faced limitations in handling complex symmetries and approximations.
Purpose of the Study:
- To implement efficient and automated computer codes for explicitly correlated coupled-cluster singles and doubles (CCSD-R12) and related methods.
- To provide benchmark correlation energies for rigorous assessment of approximate CC-R12 methods.
Main Methods:
- Implementation of CCSD-R12, CCSD(R12), and explicitly correlated second-order Moller-Plesset perturbation theory.
- Automation using computerized symbolic algebra (SMITH) to handle tensor symmetries.
- Utilizing nontruncated formalisms with resolution-of-the-identity and complementary auxiliary basis sets.
Main Results:
- Efficient computer codes for CCSD-R12 and related methods incorporating point-group symmetry.
- Benchmark CCSD-R12 correlation energies obtained using Slater-type correlation functions.
- Demonstration of the high accuracy of CCSD(R12) and CCSD(2)(R12) as approximations to CCSD-R12.
Conclusions:
- The developed codes provide reliable benchmarks for explicitly correlated methods.
- Approximate methods CCSD(R12) and CCSD(2)(R12) offer significant accuracy with reduced computational cost.
- Automated implementation facilitates advanced quantum chemical calculations.
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