Short CV
Professor of theoretical chemistry at UNamur. His research interests include the elaboration and applications of theoretical chemistry methods in the fields of linear/nonlinear optics, polymer quantum chemistry, vibrational spectroscopies, as well as material sciences. Recent achievements have targeted i) the second-, third- …- order nonlinear optical responses of molecular switches, chiral systems, diradical compounds, fluorescent proteins, air-liquid interfaces, and molecular crystals, ii) optical phenomena like thermochromism and thermally-activated delayed fluorescence, and iii) electrochemical processes at electrodes. Recently, he initiated a new direction of research, aiming at predicting reaction mechanisms, their thermodynamics and kinetics (e.g., cycloadditions, frustrated Lewis pairs, and doped amorphous silica). Some of these studies have now bridged the gap between materials sciences and life sciences. Many of these investigations are carried out within an interdisciplinary environment where the theoretical work is intertwined with the synthesis and experimental/spectroscopic characterizations. He is involved in the management of the HPC resources of UNamur and in the Fédération Wallonie Bruxelles. Since September 2025, he is vice-rector for research at UNamur.
Lecture 59: Benoît Champagne
Computing the Nonlinear Optical Responses of Molecular Crystals:
Periodic Boundary Conditions versus Multi-Scale Approaches
Benoît Champagne
Theoretical Chemistry Laboratory
Unit of Theoretical and Structural Physical Chemistry
NISM (Namur Institute of Structured Matter)
University of Namur (UNamur), B-5000 Namur, Belgium
The presentation compares the use of two, completely different, approaches to determine the second-order nonlinear optical (NLO) properties of molecular crystals, emphasizing on the strategies to account for solid state effects. On the one hand, the simulations are carried out in two steps combining i) first principles evaluations of the molecular properties (the polarizabilities and first hyperpolarizabilities) 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 in order to determine the crystal properties from the molecular ones [1]. On the other hand, the crystal second-order NLO responses are obtained in one step, adopting crystal orbital periodic boundary conditions (PBC) calculations [2]. Several aspects of these simulations (e.g. DFT with different exchange-correlation functionals versus wavefunction calculations) are discussed at the light of comparisons with experiment [1].
[1] T. Seidler, K. Stadnicka, and B. Champagne, J. Chem. Theor. Comput. 10, 2114-2124 (2014); T. Seidler, A. Krawczuk, B. Champagne, and K. Stadnicka, J. Phys. Chem. C 120, 4481-4494 (2016).
[2] F. Mairesse, L. Maschio, and B. Champagne, First Principles Evaluation of the Second Harmonic Generation Response of Reference Organic and Inorganic Crystals, J. Chem. Phys. 158, 064707 (2023); Erratum, ibidem 163, 089901 (2025)