Time-Dependent Multilevel Density Functional Theory.

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Theoretical Chemistry

Background:

• Simulating electronic excitations in complex chemical systems requires accurate modeling of environment interactions.
• Existing methods often struggle to balance accuracy and computational cost for embedded systems.

Purpose of the Study:

• To develop a novel, robust, and reliable computational approach for simulating electronic excitations.
• To accurately describe electrostatics, polarization, and non-electrostatic interactions between a target system and its environment.

Main Methods:

• A three-layer approach combining multilevel density functional theory (MLDFT) and polarizable molecular mechanics.
• Employing the polarizable fluctuating charge (FQ) force field for long-range interactions.
• Treating the embedded inactive layer as frozen to determine the target system's electronic structure.

Main Results:

• The MLDFT/FQ method accurately describes both electrostatic and non-electrostatic interactions.
• The approach successfully simulates electronic excitations of chemical systems in an external environment.
• Results show good agreement with experimental data for organic molecules in solution.

Conclusions:

• The developed MLDFT/FQ method provides a reliable tool for studying electronic excitations in condensed phases.
• This novel approach enhances the accuracy of theoretical simulations for embedded chemical systems.
• The method's validation against experimental data underscores its practical applicability.