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Updated: Aug 8, 2026
12:11
Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
Published on: April 8, 2020
Excited states in the multireference state-specific coupled-cluster theory with the complete active space reference
Vladimir V Ivanov1, Ludwik Adamowicz, Dmitry I Lyakh
1Department of Chemistry, V.N. Karazin Kharkov National University, Kharkov, Ukraine.
The Journal of Chemical Physics
|May 20, 2006
Summary
A new multireference state-specific coupled-cluster theory method accurately calculates electronically excited states. This computational chemistry approach shows promise for studying complex molecular systems, including the water molecule.
Area of Science:
- Computational Chemistry
- Quantum Chemistry
- Theoretical Chemistry
Background:
- Accurate calculation of electronically excited states is crucial for understanding molecular properties and reactions.
- Traditional methods often struggle with systems exhibiting complex electronic structures and symmetries.
Purpose of the Study:
- To develop and apply a novel multireference state-specific coupled-cluster theory (MRSSCC) method.
- To investigate electronically excited states with diverse spatial and spin symmetries.
Main Methods:
- Utilized a computerized approach for automatic generation of coupled-cluster diagrams.
- Employed a formal reference determinant to construct genuine reference states with target spin and spatial symmetries.
- Applied natural-orbital expansions of the one-electron reduced density matrix to optimize the reference function's orbital space.
Main Results:
- Successfully calculated singlet and triplet states of various spatial symmetries for the water molecule.
- Demonstrated the method's capability in handling electronic excited states through comparisons with other many-particle methods and full configuration interaction results.
Conclusions:
- The developed MRSSCC approach is effective for studying electronically excited states.
- The method shows good potential for accurate theoretical investigations of molecular excited states.
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