A non-self-consistent range-separated time-dependent density functional approach for large-scale simulations.

Area of Science:

• Computational Chemistry
• Materials Science
• Quantum Mechanics

Background:

• Time-dependent density functional theory (TDDFT) is crucial for simulating electronic excitations.
• Conventional hybrid TDDFT methods are computationally expensive, limiting large-scale applications.
• Range-separated hybrid functionals offer improved accuracy for certain electronic properties.

Purpose of the Study:

• To develop an efficient TDDFT method using range-separated hybrid functionals.
• To enable accurate and large-scale simulations of electronic excitations.
• To investigate π → π* excitations in conjugated polymers.

Main Methods:

• A non-self-consistent range-separated Hamiltonian approach for TDDFT calculations.
• Application to benchmark molecules (N2, CO, benzene, formaldehyde, ethylene-tetrafluoroethylene dimer).
• Simulation of disordered and crystalline poly(3-hexylthiophene) (P3HT) with over 600 atoms.

Main Results:

• The proposed method achieves accuracy comparable to conventional approaches for valence, Rydberg, and charge-transfer excitations.
• Accurate prediction of excitation energies and charge densities for P3HT, matching experimental data.
• Identified a significant effect of wavefunction phase on excitation energy in crystalline P3HT.

Conclusions:

• The efficient TDDFT method provides a computationally feasible route for accurate electronic excitation calculations.
• The study highlights the importance of wavefunction phase and π-π stacking in conjugated polymers.
• This method facilitates the study of complex organic materials like P3HT.