Δ Self-Consistent Field Method for Natural Anthocyanidin Dyes.

Area of Science:

• Computational chemistry
• Materials science
• Photochemistry

Background:

• Anthocyanidin dyes are crucial for applications like dye-sensitized solar cells.
• Understanding excited states is key to optimizing dye performance.
• Accurate theoretical methods are needed to study excited-state dynamics and geometry.

Purpose of the Study:

• To implement and test the Delta self-consistent field (ΔSCF) method within the DFT code CONQUEST for excited-state calculations.
• To investigate the excited-state geometry relaxation of anthocyanidin dyes.
• To study the effect of adsorption on TiO2 surfaces on the electronic and geometric properties of cyanidin.

Main Methods:

• Implementation and application of the ΔSCF method in the CONQUEST DFT code.
• Calculation of vertical excitation energies for gas-phase anthocyanidins.
• Comparison with time-dependent density functional theory (TDDFT) and experimental data.
• Adsorption of cyanidin on a TiO2 anatase (101) surface to model a dye-sensitized solar cell interface.

Main Results:

• The ΔSCF method successfully allows for atomic structure relaxation in excited states by following gradients on the excited Born-Oppenheimer surface.
• Vertical excitation energies of gas-phase anthocyanidins were computed and compared favorably with TDDFT and experimental results.
• Adsorption of cyanidin on TiO2 significantly shifted the lowest excitation energy.
• Crucial modifications in the excited-state geometry of adsorbed cyanidin were observed.

Conclusions:

• The ΔSCF method is a valuable tool for studying excited states and geometry relaxation in molecular systems.
• The study provides insights into the behavior of anthocyanidin dyes at interfaces relevant to solar cell technology.
• The findings highlight the importance of considering excited-state geometry changes for dye performance optimization.