SplitGAS Method for Strong Correlation and the Challenging Case of Cr2

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Multiconfigurational methods are essential for accurately describing electronic structures of molecules with strong electron correlation.
• Existing methods like Complete Active Space Second-Order Perturbation Theory (CASPT2) can be computationally expensive and may have limitations in accuracy.

Purpose of the Study:

• To introduce and evaluate a novel multiconfigurational quantum chemical method called Split Generalized Active Space (SplitGAS).
• To assess the performance of SplitGAS against established methods for benchmark molecular systems.

Main Methods:

• The SplitGAS method partitions the configuration interaction expansion into principal and extended parts based on an orbital criterion.
• The method was applied to study the electronic structure and properties of HF, N2, and Cr2 molecules.

Main Results:

• SplitGAS demonstrates satisfactory results for HF, N2, and particularly the challenging Cr2 molecule.
• Compared to GASSCF, SplitGAS has similar memory requirements.
• SplitGAS outperforms CASPT2 in predicting equilibrium bond length, dissociation energy, and vibrational properties.

Conclusions:

• SplitGAS is a promising new method for multiconfigurational quantum chemistry.
• The method offers a favorable balance between computational efficiency and accuracy, especially for systems requiring detailed electronic structure treatment.