Surface-induced optimal packing of two-dimensional molecular networks.
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.
Institut d'Electronique Microélectronique et Nanotechnologie (IEMN), Université de Lille I, CNRS, UMR 8520, Avenue Poincaré BP60069, 59652 Villeneuve d'Ascq, France.
Guillaume
G
Copie
Institut d'Electronique Microélectronique et Nanotechnologie (IEMN), Université de Lille I, CNRS, UMR 8520, Avenue Poincaré BP60069, 59652 Villeneuve d'Ascq, France.
Fabrizio
F
Cleri
Institut FEMTO-ST, Université de Franche-Comté, CNRS, ENSMM, 15B Avenue des Montboucons, F-25030 Besançon cedex, France.
Younes
Y
Makoudi
Département ISEN, Institut d'Electronique Microélectronique et Nanotechnologie (IEMN), CNRS, UMR 8520, 41 boulevard Vauban, 59046 Lille, France.
Christophe
C
Krzeminski
Département ISEN, Institut d'Electronique Microélectronique et Nanotechnologie (IEMN), CNRS, UMR 8520, 41 boulevard Vauban, 59046 Lille, France.
Maxime
M
Berthe
Institut FEMTO-ST, Université de Franche-Comté, CNRS, ENSMM, 15B Avenue des Montboucons, F-25030 Besançon cedex, France.
Frédéric
F
Cherioux
Institut FEMTO-ST, Université de Franche-Comté, CNRS, ENSMM, 15B Avenue des Montboucons, F-25030 Besançon cedex, France.
Frank
F
Palmino
Département ISEN, Institut d'Electronique Microélectronique et Nanotechnologie (IEMN), CNRS, UMR 8520, 41 boulevard Vauban, 59046 Lille, France.
Bruno
B
Grandidier