Séminaire

Vendredi 23 Septembre 2022 à 11h00.

Predicting and Interpreting Nonlinear Optical Responses Using Multi-Scale Approaches: Applications to Molecular Crystals and Photo-Switchable Self-Assembled Monolayers

''This seminar will discuss the elaboration and application of multi-scale methods to describe the (nonlinear) optical properties of molecular crystals, emphasizing on different strategies to account for the effects of the surrounding. Our target is the second-order nonlinear susceptibility [(2)] and more precisely the second harmonic generation response. This is part of the activities of our group aiming at better understanding nonlinear optical effects in molecules, polymers, biomolecules, solids, and interfaces, in view of applications in optoelectronic, (bio)sensing, or logic devices.
In the case of molecular crystals, the simulations are carried out by combining i) first principles evaluations of the molecular properties (the polarizability, , and the first hyperpolarizability, ) using a surrounding of point charges to describe the crystal polarizing field with ii) electrostatic interaction schemes to account for electric field screening – also called local field – effects. Several aspects of these simulations [geometry, (TD)DFT with a range of XC functionals versus wavefunction methods, vibrational contributions, crystal field] will be discussed at the light of comparisons with experiment.
Turning towards photo-switchable self-assembled monolayers, the organizational disorder of the molecules at the surface should be taken into account as well as the switching from one form to another. So, “dynamical” aspects also require to be considered and the proposed strategy consists first in performing molecular dynamics simulations before evaluating the NLO responses by enacting TDDFT calculations in combination with a simple point charge embedding scheme.

Related references
T. Seidler et al., Adv. Opt. Mater. 2, 1000-1006 (2014).
T. Seidler et al., J. Phys. Chem. C 120, 4481-4494 (2016).
K. Markey et al., J. Phys. Chem. C 121, 25509-25519 (2017)
C. Tonnelé et al., Chem. Mater. 31, 6759-6769 (2019).
L. Lescos et al., Phys. Chem. Chem. Phys. 23, 23643 -23654 (2021).
P. Beaujean et al., J. Phys. Chem. Lett. 12, 9684-9690 (2021).
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