Models of atmospheric chemistry are widely used to perform projections of future changes in the chemical composition of the global troposphere, including changes in climate related greenhouse gases and aerosol particles. However, large uncertainties are still associated with the chemistry implemented in these models, which in turn can lead to inaccurate long-term predictions.<br/>Complementary to laboratory experiments, computational modelling at the molecular level provides valuable insights on the elementary chemical and physical mechanisms. Although classical molecular dynamics (MD) can provide valuable information on growth, structure or mass accommodation of large systems, it is not possible to describe properly bond breakings involved in reactive processes. On the other hand, a full quantum mechanical treatment is not possible for systems comprising thousands of atoms.<br/>We shall present some results on the study of the reactivity of radicals such as Cl on the surface of organic aerosols composed of long carboxylic acids, using a hybrid Quantum Mechanics/Molecular Mechanics (QM/MM) scheme. The aerosol geometry is obtained from MD simulations using the Gromacs package. The QM part will be treated at the DFT level for the localization of the reactants, products, Van der Waals and transition states, followed by single point CBS/CCSD(T) energies. By sampling the surface of the aerosol, it is possible to obtain an averaged value for the rate constant, leading to an estimation of the reactive uptake coefficient.

Combining quantum chemistry with classical molecular dynamics for the theoretical study of radical reactivity at the surface of organic aerosols

256th National Meeting (2018)

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