Multi-state formulation of the frozen-density embedding quasi-diabatization approach

Area of Science:

• Quantum Chemistry
• Computational Physics
• Biochemical Modeling

Background:

• Accurate calculation of spin-density distributions is crucial for understanding molecular properties.
• Existing correlated wave function methods, like complete active space self-consistent field, are computationally expensive for large systems.
• The frozen-density embedding diabatization (FDE-diab) methodology offers a promising alternative.

Purpose of the Study:

• To implement a multi-state frozen-density embedding diabatization (FDE-diab) methodology within the Serenity program.
• To extend FDE-diab for coupling multiple charge-localized quasi-diabatic states.
• To enable efficient calculations of ground and excited state spin-density distributions and excitation energies.

Main Methods:

• Multi-state implementation of the FDE-diab methodology.
• Coupling of an arbitrary number of quasi-diabatic states.
• Development of approximate computational schemes to reduce computational cost.
• Comparison with correlated wave function approaches (e.g., complete active space self-consistent field).

Main Results:

• The FDE-diab implementation successfully calculates ground and excited state spin-density distributions and excitation energies.
• Achieved results comparable to correlated wave function methods but with significantly lower computational effort.
• Demonstrated approximate schemes that systematically converge to the full FDE-diab solution.
• Validated the efficiency and accuracy of the new computational framework.

Conclusions:

• The developed multi-state FDE-diab methodology provides an efficient and accurate tool for calculating spin-density distributions.
• This approach significantly reduces computational cost, making it suitable for large molecular systems.
• Enables advanced computational studies on spin-density distributions and related properties in biochemically relevant molecules.