Modeling solvation effects in real-space and real-time within density functional approaches

Area of Science:

• Computational chemistry
• Quantum chemistry
• Physical chemistry

Background:

• The Polarizable Continuum Model (PCM) is crucial for simulating molecules in solvents using Density Functional Theory (DFT).
• Existing methods face challenges with real-space (TD)DFT calculations due to potential singularities when representing solvent effects.
• Accurate modeling of solvation is essential for understanding and predicting molecular behavior in liquid environments.

Purpose of the Study:

• To develop a novel methodology for incorporating solvation effects into real-space (TD)DFT simulations.
• To address and regularize Coulomb singularities arising in real-space solvent potential calculations.
• To provide accurate predictions of electronic and optical properties for molecules in dielectric media.

Main Methods:

• Implementation of the Polarizable Continuum Model (PCM) within a real-space framework.
• Utilizing the boundary element method to compute solvent reaction potentials.
• Regularizing Coulomb singularities using spherical Gaussian functions to distribute apparent charges.
• Integration of the method into the Octopus computational chemistry code.

Main Results:

• Successfully implemented a real-space PCM approach for (TD)DFT.
• Demonstrated a robust method for regularizing singularities near the solute-solvent interface.
• Obtained accurate solvation free energies and solvatochromic shifts for organic molecules in water.

Conclusions:

• The developed real-space methodology effectively captures solvation effects in (TD)DFT.
• The Gaussian charge distribution approach successfully regularizes singularities, enhancing computational accuracy.
• This work provides a valuable tool for studying molecular properties in solution, particularly for complex systems.