Toward improved density functionals for the correlation energy.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Accurate prediction of electron correlation energies is crucial for understanding atomic and molecular properties.
• Existing density functionals often struggle with heavier elements and closed-shell systems.
• Developing improved functionals is essential for advancing computational chemistry.

Purpose of the Study:

• To evaluate the performance of eleven widely used density functionals for predicting nonrelativistic electron correlation energies.
• To develop novel, few-parameter density functionals for improved accuracy, especially for heavier atoms.
• To assess the impact of reparametrization on the performance of existing functionals.

Main Methods:

• Testing eleven established density functionals on atoms (He-Ar), cations (Li+-K+), and (1)S state atoms (Ca-Rn).
• Heuristically developing several new, few-parameter density functionals.
• Reparametrizing existing functionals to assess performance improvements.

Main Results:

• Existing density functionals exhibit poor performance for heavier atoms.
• Reparametrization enhances accuracy for light atoms but not for heavier, closed-shell atoms.
• Four newly developed functionals demonstrate qualitatively improved predictions for heavier atoms without sacrificing accuracy for lighter ones.

Conclusions:

• Novel density functionals offer a promising approach to accurately predict electron correlation energies for a wider range of atoms.
• Further advancements require reliable electron correlation energy data for more atoms, particularly heavy ones.
• The developed functionals represent a step forward in computational chemistry for electronic structure calculations.