Fully Polarizable Multiconfigurational Self-Consistent Field/Fluctuating Charges Approach.

Area of Science:

• Computational Chemistry
• Theoretical Chemistry
• Physical Chemistry

Background:

• Accurate simulation of molecular behavior in solution is crucial for understanding chemical processes.
• Existing models often struggle to capture the complex interplay between solute and solvent dynamics.
• Developing robust multiscale models is essential for bridging quantum mechanical and classical descriptions.

Purpose of the Study:

• To present a novel multiscale model coupling the multiconfigurational self-consistent field (MCSCF) method with the fluctuating charges (FQ) force field.
• To validate the MCSCF/FQ approach for calculating vertical excitation energies in aqueous solution.
• To integrate the model with molecular dynamics for capturing conformational changes and dynamic solvation.

Main Methods:

• Coupling of MCSCF quantum mechanics with a classical atomistic polarizable FQ force field.
• Application of the CASSCF (Complete Active Space Self-Consistent Field) scheme for energy calculations.
• Integration with molecular dynamics (MD) simulations to study dynamic solvation and conformational changes.

Main Results:

• The MCSCF/FQ model was successfully applied to compute vertical excitation energies for formaldehyde and para-nitroaniline in aqueous solution.
• The integrated approach captured solute conformational changes and dynamic solvation effects.
• Comparative analysis demonstrated the model's accuracy in reproducing solute-solvent interactions and spectral signals.

Conclusions:

• The presented MCSCF/FQ multiscale model offers a powerful tool for studying molecular systems in solution.
• The model accurately reproduces solute-solvent interactions and spectral properties, validated against experimental data.
• This approach provides valuable insights into the dynamic aspects of solvation and molecular behavior.