The density matrix functional approach to electron correlation: dynamic and nondynamic correlation along the full...

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Accurate description of bond weakening and breaking is crucial in chemistry.
• Density matrix functionals offer advantages over density functionals by naturally incorporating nondynamical and dynamical correlation.
• The Löwdin-Shull functional is an exact natural orbital functional for two-electron systems.

Purpose of the Study:

• To extend the Löwdin-Shull functional for describing single electron pair bond breaking in N-electron molecules.
• To investigate the application of these extended functionals using LiH, BeH(+), and Li2 as model systems.
• To ensure proper formulation of the functional, including L integrals for response function calculations.

Main Methods:

• Development of extended Löwdin-Shull functionals for N-electron systems.
• Inclusion of J, K, and L integrals in the functional formulation.
• Utilizing full Configuration Interaction (CI) calculations as a benchmark.
• Testing on prototype molecules like LiH, BeH(+), and Li2.

Main Results:

• Accurate energy curves were obtained along the complete dissociation coordinate.
• The extended functionals successfully described bond breaking processes.
• The formulation including L integrals proved crucial for response function calculations.

Conclusions:

• Extended Löwdin-Shull functionals provide an accurate method for describing bond breaking in N-electron molecules.
• The inclusion of L integrals is essential for accurate response function calculations.
• This work advances the capability of density matrix functionals in computational chemistry.