Direct orbital selection for projection-based embedding

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Method Development

Background:

• Projection-based embedding (PbE) is a robust method for accurate electronic structure calculations.
• PbE combines sophisticated methods for reaction centers with cost-effective DFT for environments.
• Current PbE methods often require manual selection of 'active atoms'.

Purpose of the Study:

• To develop an automated, inexpensive approach for selecting active orbitals in PbE.
• To eliminate the need for specifying 'active atoms' in PbE calculations.
• To investigate and compare different orbital selection schemes for PbE.

Main Methods:

• Developed an automatic orbital selection strategy based on orbital changes during a reaction.
• Applied the method to PBE0-in-PBE embedding, comparing variants based on orbitalwise partial charges and kinetic energy.
• Evaluated performance using shellwise intrinsic atomic orbital charges for six different reaction types.

Main Results:

• The proposed automatic orbital selection method effectively identifies orbitals active during a reaction.
• Shellwise intrinsic atomic orbital charges proved to be the most successful selection scheme.
• Errors in calculated reaction energies and barriers rapidly decreased as the active orbital space expanded.

Conclusions:

• The automated orbital selection approach is a significant improvement over atom-based selection in PbE.
• This method enhances the accuracy and efficiency of reaction barrier and energy calculations.
• The findings pave the way for more accessible and reliable computational chemistry studies.