Development of Large-Scale Excited-State Calculations Based on the Divide-and-Conquer Time-Dependent Density...

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Theoretical Chemistry

Background:

• Accurate excited-state calculations are crucial for understanding photophysical processes.
• Traditional methods struggle with computational cost for large molecular systems.
• Time-dependent density functional tight-binding (TDDFTB) offers a balance of accuracy and efficiency.

Purpose of the Study:

• To extend the divide-and-conquer (DC) method to TDDFTB theory for large-scale excited-state calculations.
• To implement efficient diagonalization algorithms for TDDFTB and DC-TDDFTB.
• To validate the developed DC-TDDFTB method for accuracy and efficiency.

Main Methods:

• Development and implementation of the divide-and-conquer TDDFTB (DC-TDDFTB) method.
• Integration of efficient diagonalization algorithms into an in-house computational program.
• Application of DC-TDDFTB to polyethylene aldehyde and p-coumaric acid in water.
• TDDFTB metadynamics simulations for acridinium in ground and excited states.

Main Results:

• The DC-TDDFTB method demonstrated high accuracy and efficiency in excited-state calculations.
• Test calculations on polyethylene aldehyde and p-coumaric acid validated the method's performance.
• Metadynamics simulations provided reasonable pKa values for acridinium, comparable to experimental data.

Conclusions:

• The developed DC-TDDFTB method is a powerful tool for accurate and efficient excited-state calculations of large systems.
• The method shows promise for studying complex molecular systems and photochemical reactions.
• DC-TDDFTB can be applied to investigate properties like pKa in different electronic states.