Starting SCF calculations by superposition of atomic densities

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Self-Consistent Field (SCF) calculations are fundamental in quantum chemistry.
• Direct SCF methods offer computational advantages but require careful initialization.
• Starting SCF calculations from atomic electron densities is a known technique for closed-shell systems.

Purpose of the Study:

• To describe and evaluate a general procedure for initiating SCF calculations using a sum of atomic electron densities.
• To demonstrate the applicability and advantages of this method for open-shell systems.
• To compare the proposed method with alternative starting procedures.

Main Methods:

• Implementation of the atomic electron density summation procedure in the GAMESS-UK computational chemistry software.
• Testing the procedure with various open-shell species.
• Comparison of convergence behavior and computational efficiency against traditional starting methods.

Main Results:

• The procedure is shown to be effective for general SCF calculations, including open-shell systems.
• It eliminates the need to pre-converge closed-shell Hartree-Fock calculations for open-shell species.
• The method demonstrates superior performance compared to starting from converged minimal basis calculations or bare nucleus Hamiltonians.

Conclusions:

• Initiating SCF calculations from atomic electron densities provides a more straightforward and efficient approach, particularly for open-shell systems.
• This method enhances the practicality of computational chemistry workflows.
• The GAMESS-UK implementation offers a robust tool for researchers in the field.