Second harmonic generation responses of ion pairs forming dimeric aggregates

Frequently observed in liquid solutions, the aggregation effects can modulate the second- and third-order optical (NLO) responses due to induced global symmetry changes. To better understand this effect, we applied, for the first time, a sequential multiscale approach – combining molecular dynamics and density functional theory calculations – to unravel the dimerization effects on the second harmonic generation responses for a set of anion-cation pairs. Our simulations provided different structural shapes for dimers as stacked, L, and head-to-head ones, something hard to identify in experimental measurements.


From the NLO point of view, the dimerization reduced the response by half for L-shaped and by only 10 % for stacked-shaped configurations, allowing deeper explanations about the concentration-dependence observed by Tessore1. Thereby, we demonstrated that a multiscale simulation is a great tool to better understand the NLO properties of anion-cation pairs in a liquid environment.

1 - F. Tessore, E. Cariati, F. Cariati, D. Roberto, R. Ugo, P. Mussini, C. Zuccaccia, A. Macchioni, ChemPhysChem. 11 (2010) 495–507.

Tárcius N. Ramos hold a postdoctoral position supported by “Fonds Spécial de Recherche of UNamur”. All calculations were performed on the computers of the “Consortium des Équipements de Calcul Intensif (CÉCI)” (, including those of the “UNamur Technological Platform of High-Performance Computing (PTCI)” (