Multiconfiguration Pair-Density Functional Theory.

Area of Science:

• Quantum Chemistry
• Theoretical Chemistry
• Computational Chemistry

Background:

• Density Functional Theory (DFT) typically relies on electron density and its gradient.
• Accurate calculation of electronic energies often requires computationally expensive multireference methods.
• Existing DFT functionals struggle with systems exhibiting strong electron correlation.

Purpose of the Study:

• To develop a new theoretical framework, MC-PDFT, that combines the strengths of multiconfigurational methods and DFT.
• To extend DFT by incorporating the on-top pair density as a key component.
• To provide a more accurate and computationally efficient method for electronic structure calculations.

Main Methods:

• Developed Multiconfiguration Pair-Density Functional Theory (MC-PDFT).
• Employed multiconfigurational self-consistent-field (MCSCF) wave functions to compute electron density, its gradient, and on-top pair density.
• Utilized a functional of these quantities to determine the remaining energy contributions.

Main Results:

• MC-PDFT successfully calculates bond energies, potential energy curves, and electronic excitation energies for various molecules and atoms.
• The method demonstrates quantitative accuracy comparable to more expensive multireference perturbation theory.
• Computational cost and scaling are similar to MCSCF.

Conclusions:

• MC-PDFT offers a promising new avenue for accurate electronic structure calculations.
• The framework goes beyond the Hohenberg-Kohn theorem by including the on-top pair density.
• MC-PDFT provides a computationally efficient approach to achieve high accuracy in quantum chemistry.