Quadratic Response Properties from TDDFT: Trials and Tribulations

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Spectroscopy

Background:

• Nonlinear optical properties are crucial for materials science and molecular design.
• Accurate theoretical prediction of these properties is computationally demanding.
• Time-dependent density functional theory (TDDFT) offers a promising framework for such calculations.

Purpose of the Study:

• To develop and implement an efficient TDDFT method for calculating quadratic response properties.
• To enable accurate prediction of static and dynamic dipole hyperpolarizability and two-photon absorption amplitudes.
• To provide a computationally feasible tool for studying complex molecular systems.

Main Methods:

• Efficient turbomole implementation of quadratic response properties within TDDFT.
• Full utilization of point-group and permutational symmetry.
• Calculation of nonlinear properties using hybrid density functionals for large molecules.
• Pseudowavefunction approach for excited-state absorption spectra.

Main Results:

• Accurate computation of static and dynamic dipole hyperpolarizability.
• Reproduction of two-photon absorption cross sections for twisted porphyrin chains.
• Simulation of hyper-Raleigh scattering signals consistent with experimental data for calix[4]arene stereoisomers.
• Demonstration of qualitative features in excited-state absorption spectra.

Conclusions:

• The developed TDDFT method efficiently calculates important nonlinear optical properties for large molecules.
• The implementation accurately reproduces experimental and theoretical data for various molecular systems.
• Addressing the pole structure of adiabatic TDDFT is crucial for accurate excited-state spectra and hyperpolarizabilities.