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Excitonic Hamiltonians for Calculating Optical Absorption Spectra and Optoelectronic Properties of Molecular Aggregates and Solids
Published on: May 27, 2020
Two-Photon Absorption of Quadrupolar Dyes: Performance of Density Functional Approximations
Karan Ahmadzadeh1, Robert Zaleśny2, Wei Hu3
1Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui230026, China.
Journal of Chemical Theory and Computation
|July 14, 2026
Summary
We evaluated exchange-correlation functionals for two-photon absorption (2PA) in quadrupolar dyes. MN15 and higher-exact-exchange hybrids offer balanced performance, with MN15 showing the lowest global error.
Area of Science:
- Computational Chemistry
- Quantum Chemistry
- Spectroscopy
Background:
- Two-photon absorption (2PA) is crucial for materials with nonlinear optical properties.
- Centrosymmetric quadrupolar dyes exhibit unique 2PA pathways (Ag → Au → Ag) due to their symmetry.
- Accurate theoretical prediction of 2PA strengths is essential for designing novel materials.
Purpose of the Study:
- To benchmark various exchange-correlation (XC) functionals for predicting 2PA strengths in centrosymmetric quadrupolar dyes.
- To identify functionals that accurately capture the structure-property relationships and absolute magnitudes of 2PA.
- To understand the origins of discrepancies between theoretical predictions and reference calculations.
Main Methods:
- Time-Dependent Density Functional Theory (TD-DFT) calculations were employed.
- A representative set of XC functionals was benchmarked against CC2 reference calculations.
- A three-state framework was used to analyze the 2PA response.
Main Results:
- Many XC functionals qualitatively reproduced the CC2 structure-property trends.
- Substantial deviations in absolute 2PA magnitudes were observed, primarily due to transition dipole moment errors.
- Higher-exact-exchange hybrids (MN15, BMK, M06-2X, BH&HLYP) showed balanced performance, with MN15 achieving the lowest global error.
Conclusions:
- TD-DFT can capture the main chemical effects governing 2PA in these systems.
- XC functional choice significantly impacts the accuracy of predicted 2PA strengths, especially absolute values.
- MN15 and other higher-exact-exchange hybrids are recommended for accurate 2PA calculations of quadrupolar dyes.
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