Molecular Modeling of Aerosols

PhD: Josip Lovric
(defended on 16th June 2017)

In this thesis numerical methods are used to study the properties, described at the molecular level, of organic aerosols, especially marine aerosols, and their interaction with species in the atmosphere. The organisation of the organic matter in these aerosols plays a key role for their optical, chemical properties, and their ability to act as a cloud condensation nuclei.

The first part reviews atmospheric context and the methods (classical molecular dynamics and hybrid quantum/classical approaches) used in this thesis. Then applications to three cases are detailed.
Firstly, the organization, more particularly the orientation, of palmitic acid molecules adsorbed on a salt (NaCl) surface as a function of the fatty acid coverage and temperature has been studied using classical molecular dynamics (Gromacs package). The impact of the humidity on the structuration of this organic coating has been described in details, showing the existence of structured fatty acid island-like monolayers on NaCl surface.

In a second study, the reactivity of NO2 with these heterogeneous marine aerosols has been investigated by a hybrid quantum/classical method (CP2K package), with taking into account the effect of the humidity.
The last study is a classical molecular dynamics of n-butanol crystal, water accommodation at these surfaces and simulation of water jet collision with n-butanol surface. These simulations, complementary to experiments, were performed to better understand the fundamental role of the water-organic matter interaction on the properties of the aerosols and clouds.

- President of the jury : Thérèse Huet, Professeur - Université de Lille
- Thesis supervisor : dr. Stéphane Briquez
- Thesis co-supervisor(s) : dr. Denis Duflot
- Referees : Jan Pettersson, Professeur - University of Gothenburg ; Sylvain Picaud, Directeur de Recherches CNRS – Université de France- Comté
- Examiner : Sophie Sobanska, Chargée de Recherches CNRS – Université de Bordeaux

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Keywords: molecular interactions, aerosols, surface, atmosphere, halogen, salt.

Fundings: Région Nord Pas de Calais / Labex CaPPA

Responsibles: S. BRIQUEZ, B. POUILLY

Laboratory: PhLAM