Configuration interaction based on constrained density functional theory: a multireference method.

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Materials Science

Background:

• Density Functional Theory (DFT) excels at dynamic correlation but struggles with static correlation in near-degenerate systems.
• Static correlation is crucial for accurately describing bond breaking and forming processes.
• Existing methods often fail to capture the nuances of both correlation types simultaneously.

Purpose of the Study:

• To develop a novel computational method integrating Configuration Interaction (CI) and DFT.
• To accurately treat systems dominated by static correlation using a multireference approach.
• To improve the description of chemical bond dynamics.

Main Methods:

• A constrained DFT approach is used to create localized charge or spin states for an active space.
• An effective Hamiltonian matrix is constructed within this localized active space.
• A Configuration Interaction (CI) step is applied to recover static correlation from localized reference states.

Main Results:

• The proposed method successfully treats static correlation using localized configurations.
• Dynamic correlation is efficiently captured by incorporating DFT functionals.
• Accurate ground-state dissociation curves for H(2)(+), H(2), and LiF were obtained, validating the approach.

Conclusions:

• The new CI-DFT method offers a robust way to handle both static and dynamic correlation.
• This technique provides accurate descriptions of bond breaking and forming, crucial for chemical reaction studies.
• The method shows significant promise for advancing computational chemistry and materials science.