Combining ab-initio and classical molecular dynamics simulations to unravel the structure of the 2D-HB-network at the air-water interface

Alessandra Serva , Simone Pezzotti (1) , Sana Bougueroua (1) , Daria Ruth Galimberti (1) , Marie-Pierre Gaigeot (1)

1 LAMBE - Laboratoire Analyse et Modélisation pour la Biologie et l'Environnement

An extensive structural characterization of the 2D-HB-Network formed by water molecules at the air-water interface has been carried out by means of DFT-based and classical molecular dynamics simulations. SPC/E and SPC/Fw force fields commonly used for modelling liquid water are shown to correctly reproduce the 2D-HB-Network structure obtained from the reference ab-initio simulation. For both DFT-MD and classical MD representations, identical results have been obtained by increasing the size and time-scale of the simulations, starting from a simulation box of 256 water molecules in the liquid phase, simulated for 20 ps up to 25 ns. One pivotal result is that ∼90% of the water molecules in the interfacial layer are connected by a collective and extended net of HBs oriented parallel to the surface, and this 2D-HB-Network is built upon adjacent water rings mostly formed by 4, 5 or 6 water molecules. This finding in particular rationalizes previous non linear SFG spectroscopic results suggesting that liquid water at the interface with hydrophobic media could arrange in rings.

Keywords: Air/water interface; DFT-MD; AIMD; H-Bond network

Domains: Chemical Sciences; Cheminformatics; Theoretical and/or physical chemistry; Computational Geometry [cs.CG]

Alessandra Serva, Simone Pezzotti, Sana Bougueroua, Daria Ruth Galimberti, Marie-Pierre Gaigeot. Combining ab-initio and classical molecular dynamics simulations to unravel the structure of the 2D-HB-network at the air-water interface. Journal of Molecular Structure, 2018, 1165, pp.71-78. ⟨10.1016/j.molstruc.2018.03.074⟩. ⟨hal-02082460⟩