Combining frozen-density embedding with the conductor-like screening model using Lagrangian techniques for response...

Area of Science:

• Computational Chemistry
• Theoretical Chemistry
• Quantum Chemistry

Background:

• Accurate molecular modeling in complex environments is crucial for understanding chemical processes.
• Existing methods often struggle to balance computational cost with accuracy for large systems.
• Multiscale approaches offer a promising avenue for efficient and reliable simulations.

Purpose of the Study:

• To derive and present a rigorous multiscale approach combining frozen-density embedding (FDE) with continuum solvation models.
• To enable accurate calculations of ground- and excited-state properties for molecules in complex environments.
• To demonstrate the application of this method for electronic excitation energies and molecular gradients.

Main Methods:

• The study employs a variational Lagrangian framework for the explicit derivation of the FDE+COSMO method.
• Analytical molecular gradients are derived for excited states (Tamm-Dancoff approximation) and ground states (MP2, CC2).
• The approach combines atomistic FDE with continuum solvation (e.g., conductor-like screening model - COSMO).

Main Results:

• The FDE+COSMO method accurately describes vertical electronic excitation (VEE) energies and Stokes shifts for uracil in water and carbostyril in DMSO.
• Calculations on simplified protein models demonstrate the method's applicability to larger systems.
• Interaction terms between FDE and continuum significantly influence excitation energies (up to 0.3 eV), necessitating their inclusion.

Conclusions:

• The developed FDE+COSMO approach provides a rigorous and accurate multiscale method for molecular modeling in complex environments.
• This work represents a significant advancement towards ab initio multilayer and multiscale modeling.
• The inclusion of continuum effects is essential for precise calculations of electronic properties.