Nonempirical Adiabatic Connection Correlation Functional from Hartree-Fock Orbitals

Area of Science:

• Quantum Chemistry
• Computational Materials Science
• Theoretical Physics

Background:

• Accurate description of electron correlation is crucial for predicting molecular and material properties.
• Existing methods like Møller-Plesset perturbation theory (MP2) have limitations, particularly in strong interaction regimes.
• Nonempirical functionals offer a systematic way to improve upon approximate methods without empirical fitting.

Purpose of the Study:

• To develop a novel nonempirical correlation functional based on the adiabatic connection formalism.
• To ensure the functional satisfies both weak and strong interaction limits and accurately models the uniform electron gas.
• To generalize post-Hartree-Fock (HF) methods with nonlinear contributions and strong correlation ingredients.

Main Methods:

• Constructed a correlation functional rooted in the Møller-Plesset (MP) adiabatic connection (AC) formalism.
• Utilized Hartree-Fock (HF) orbitals and employed the uniform electron gas (UEG) and helium atom as model systems.
• Generalized second-order perturbation theory (MP2) correlation with nonlinear contributions.

Main Results:

• The developed functional accurately describes electron correlation in atoms with 1 mHa/electron accuracy.
• Achieved accuracy for jellium surface energies and corrected MP2 overbinding without error cancellation.
• Demonstrated excellent performance across diverse systems and properties, including atomization/interaction energies and ionization potentials.

Conclusions:

• The nonempirical strategy provides a robust and accurate method for calculating electron correlation.
• The functional represents a significant advancement over standard post-HF methods, particularly MP2.
• This work paves the way for a new generation of density functionals incorporating nonlinear MP2 and strong correlation effects.