Electron correlation by polarization of interacting densities.

Area of Science:

• Computational chemistry
• Quantum chemistry
• Electronic structure theory

Background:

• Accurate electronic structure calculations are crucial for understanding chemical phenomena.
• Dynamical correlation effects significantly impact the accuracy of theoretical models.
• Current methods often require computationally expensive basis set expansions.

Purpose of the Study:

• To develop a computationally efficient method for incorporating dynamical correlation into electronic structure calculations.
• To reduce the magnitude of Coulomb interactions in quantum chemical computations.
• To avoid the explicit inclusion of higher spherical harmonic functions in molecular orbital basis sets.

Main Methods:

• Correlating Coulomb interactions by dynamically polarizing basis function components of interacting densities.
• Decomposing molecular orbital densities into spherical components.
• Treating interacting components as two-electron wavefunctions within an average field Hamiltonian plus r12^-1.
• Implementing the modified Coulomb interactions in single-determinant or configuration interaction calculations.

Main Results:

• The proposed method dynamically correlates Coulomb interactions, reducing their magnitude.
• Exchange integrals of molecular orbitals remain uncorrelated.
• The approach effectively accounts for dynamical correlation without basis set augmentation.
• A method for avoiding redundancy in calculations is presented.

Conclusions:

• The developed method offers an efficient way to include dynamical correlation in electronic structure calculations.
• This technique can be applied to various systems, including atoms, ions, and molecules with diverse bonding and spin states.
• The approach provides a balance between accuracy and computational cost for quantum chemical studies.