Focal-point approach with pair-specific cusp correction for coupled-cluster theory

Area of Science:

• Quantum Chemistry
• Computational Physics

Background:

• Coupled-cluster singles and doubles (CCSD) methods are crucial for accurate electronic structure calculations.
• Basis set incompleteness error (BSIE) significantly impacts the accuracy of correlated electronic energies.

Purpose of the Study:

• To develop an efficient and accurate basis set correction scheme for CCSD.
• To reduce the computational cost associated with achieving high accuracy in quantum chemical calculations.

Main Methods:

• Employing frozen natural orbitals (FNOs) and diagrammatically decomposed contributions to electronic correlation energy.
• Deriving a simple approximation for the BSIE of the particle-particle ladder term in CCSD.
• Implementing a rescaled pair-specific MP2 BSIE correction.

Main Results:

• Demonstrated effectiveness for the uniform electron gas.
• Achieved rapidly convergent reaction energies, atomization energies, electron affinities, and ionization potentials for atoms and molecules.
• Showcased an excellent trade-off between virtual orbital basis set size and remaining BSIEs for CCSD(T) calculations.

Conclusions:

• The proposed basis set correction scheme significantly improves the accuracy of CCSD calculations.
• The method is computationally efficient and easily implementable.
• It enables accurate predictions of molecular properties with reduced basis set requirements.