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Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry
Published on: April 8, 2020
Surface-induced optimal packing of two-dimensional molecular networks
Guillaume Copie1, Fabrizio Cleri1, Younes Makoudi2
1Institut d'Electronique Microélectronique et Nanotechnologie (IEMN), Université de Lille I, CNRS, UMR 8520, Avenue Poincaré BP60069, 59652 Villeneuve d'Ascq, France.
Abstract:
High-density packing in organic crystals is usually associated with an increase of the coordination between molecules. Such a concept is not necessarily extended to two-dimensional molecular networks self-assembled on a solid surface, for which we demonstrate the key role of the surface in inducing the optimal packing. By a combination of scanning tunneling microscopy experiments and multiscale computer simulations, we study the phase transition between two polymorphs. We find that, contrary to intuition, the structure with the lowest packing fraction corresponds to the highest molecular coordination number, due to the competition between surface and intermolecular forces. Having the lowest free energy, this structure spreads out as the most stable polymorph over a wide range of molecular concentrations.
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