Efficient Multiconfigurational Quantum Chemistry Approach to Single-Ion Magnets Based on Density Matrix Embedding...

Area of Science:

• Computational Quantum Chemistry
• Materials Science
• Molecular Magnetism

Background:

• Strongly correlated systems pose significant challenges for traditional quantum chemistry methods.
• Accurate theoretical descriptions are needed for molecular magnets, particularly single-ion magnets (SIMs).
• Existing methods often face high computational costs for complex systems.

Purpose of the Study:

• To develop an efficient quantum embedding approach for studying strongly correlated systems.
• To apply this approach to the theoretical description of single-ion magnets (SIMs).
• To accurately determine zero-field splitting parameters in SIMs.

Main Methods:

• Combined Density Matrix Embedding Theory (DMET) with Complete Active Space Self-Consistent Field and spin-orbit coupling (CASSI-SO).
• Developed a novel regularized direct inversion of iterative subspace (R-DIIS) technique for stable restricted open-shell Hartree-Fock calculations.
• Applied the DMET+CASSI-SO approach to model 3d-SIMs.

Main Results:

• The R-DIIS technique ensures convergence to a physically correct ground state, crucial for subsequent CASSI-SO calculations.
• The DMET+CASSI-SO approach yields reliable zero-field splitting parameters for 3d-SIMs.
• Achieved a dramatic reduction in computational cost compared to all-electron methods.

Conclusions:

• The proposed DMET+CASSI-SO method is a computationally efficient and accurate tool for studying SIMs.
• This work highlights the potential of DMET-based multiconfigurational approaches for investigating magneto-structural correlations in complex molecular magnets.
• The developed R-DIIS technique enhances the reliability of quantum embedding calculations for open-shell systems.