Explicitly correlated coupled-cluster theory for static polarizabilities

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Molecular Modeling

Background:

• Accurate calculation of static polarizabilities is crucial for understanding molecular responses to electric fields.
• Traditional coupled-cluster methods can be computationally expensive and may lack sufficient accuracy for certain properties.

Purpose of the Study:

• To develop and implement an explicitly correlated coupled-cluster singles and doubles [CCSD(F12)] method for calculating static polarizabilities.
• To improve the accuracy of static polarizability calculations by incorporating a modified ansatz for geminal parts of cluster operators.

Main Methods:

• Formulation and implementation of a linearly approximated explicitly correlated CCSD(F12) model.
• Introduction of a modified ansatz for the geminal part of cluster operators to balance perturbed and unperturbed wave functions.
• Derivation and implementation of an explicitly correlated version of coupled-perturbed CCSD equations.

Main Results:

• The developed method provides accurate static polarizabilities for molecules.
• Numerical tests on eight molecules show good agreement with complete basis set CCSD results.
• The explicitly correlated approach achieves high accuracy even at the triple-ζ basis set level.

Conclusions:

• The new explicitly correlated CCSD(F12) method offers a significant improvement in the accuracy of static polarizability calculations.
• This approach provides a balanced description of electronic wave functions, leading to more reliable predictions.
• The method is computationally efficient and accurate, making it valuable for molecular property studies.