Particle-particle ladder based basis-set corrections applied to atoms and molecules using coupled-cluster theory

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Coupled cluster theory is a powerful method for calculating electronic correlation energies.
• Basis set incompleteness is a known limitation in computational chemistry.
• Accurate calculations often require large basis sets, increasing computational cost.

Purpose of the Study:

• To investigate the basis-set convergence of electronic correlation energies using a novel finite basis-set correction technique.
• To assess the accuracy of the correction technique for atomic and molecular systems.
• To determine the feasibility of reducing basis set sizes without compromising accuracy.

Main Methods:

• Applied a finite basis-set correction to the diagrammatically decomposed coupled cluster singles and doubles (CCSD) correlation energy.
• Focused correction on the second-order energy and particle-particle ladder term.
• Evaluated the technique on a large benchmark set of atomic and molecular properties.

Main Results:

• Basis set reductions by two cardinal numbers are possible for atomization energies, ionization potentials, and electron affinities.
• Accuracy is maintained when compared to conventional CCSD calculations with larger basis sets.
• For reaction energies, basis set reductions by one cardinal number are feasible.

Conclusions:

• The proposed finite basis-set correction technique effectively reduces the required basis set size for accurate electronic structure calculations.
• This method offers a computationally efficient alternative to traditional coupled cluster calculations.
• The technique is versatile and can be extended to other many-electron theories without requiring higher-order integrals.