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Published on: April 8, 2020
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A configuration interaction correction on top of pair coupled cluster doubles
Artur Nowak1, Katharina Boguslawski1
1Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University in Toruń, Grudziadzka 5, 87-100 Toruń, Poland. k.boguslawski@fizyka.umk.pl.
Physical Chemistry Chemical Physics : PCCP
|February 22, 2023
Summary
Geminal-based methods, like pair coupled cluster doubles (pCCD) with configuration interaction (CI) extensions, offer accurate modeling for strongly correlated systems. Including a Davidson correction significantly improves spectroscopic constants for these challenging chemical compounds.
Area of Science:
- Computational Chemistry
- Quantum Chemistry
- Theoretical Chemistry
Background:
- Geminal-based methods show promise for modeling strongly correlated systems efficiently.
- Dynamical correlation effects and broken-pair states are key challenges in these models.
- Existing strategies often use a posteriori corrections to address missing correlation effects.
Purpose of the Study:
- To scrutinize the accuracy of pair coupled cluster doubles (pCCD) method enhanced by configuration interaction (CI) theory.
- To benchmark various pCCD-CI models against conventional coupled-cluster (CC) methods and Davidson corrections.
- To assess the performance of these advanced methods for challenging molecular systems.
Main Methods:
- Implementation and testing of pCCD extended with configuration interaction (CI) models.
- Benchmarking against coupled-cluster singles and doubles (CCSD) and other CC corrections.
- Inclusion and evaluation of a Davidson correction for improved accuracy.
Main Results:
- pCCD-CI approaches, particularly with a Davidson correction, significantly improve spectroscopic constants.
- These methods show improved accuracy compared to conventional coupled-cluster methods for N2, F2, and actinide compounds.
- The accuracy of the tested pCCD-CI variants falls between linearized frozen pCCD and frozen pCCD.
Conclusions:
- Pair coupled cluster doubles (pCCD) combined with configuration interaction (CI) offers a viable route to accurate modeling of strongly correlated systems.
- The inclusion of a Davidson correction is crucial for achieving substantial improvements in spectroscopic properties.
- These enhanced geminal-based methods provide a valuable alternative to traditional quantum chemical approaches for complex molecules.
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