Molecular Dynamics Simulation Study of Water Surfaces: Comparison of Flexible Water Models

Abstract

Molecular dynamics (MD) simulation has been used extensively to study water surfaces. Nevertheless, the quantitative prediction of water surface tension has been controversial, since results from different simulation studies using the same water model may differ considerably. Recent research has suggested that bond flexibility, long-range electrostatic interactions, and certain simulation parameters, such as Lennard-Jones (LJ) cutoff distance and simulation time, may play an important role in determining the simulated surface tension. To gain better insight on the MD simulation of water surfaces, particularly on the prediction of surface tension, we examined seven flexible water models using a consistent set of simulation parameters. The surface tensions of the flexible, extended simple point charge (SPCE-F) model and the flexible three-center (F3C) model at 300 K were found to be 70.2 and 65.3 mN/m, respectively, in reasonable agreement with the experimental value of 71.7 mN/m. More importantly, however, detailed analysis of the interfacial structure and contributions from various interactions have revealed that the surface tension of water is determined by the delicate balance between intramolecular (bond stretching) and intermolecular (LJ) interactions, which reflects both the molecular orientation in the interfacial region and the density variation across the Gibbs dividing surface (GDS). In addition, the water molecules on the liquid side of the GDS were found to lie almost parallel to the surface, which helps to clarify the dual-layer structure suggested by sum-frequency generation spectroscopy. By correlating the simulated surface tensions of the seven water models with selected molecular parameters, it was found that the partial charge distribution in the water molecule is likely a key factor in determining the near-parallel alignment of water molecules with the surface.

Amino acids in atmospheric droplets: perturbation of surface tension and critical supersaturation predicted by computer simulations

“…A versatile theoretical approach to investigate liquid-gas interfaces at the molecular level is the molecular dynamics (MD) simulation technique, which has become more and more useful due to the fast development of algorithms and computers. Starting from the pioneer paper by Alejandre et al (1995) MD simulations on surface tension have been extensive for planar liquid-gas interfaces (Yeh and Berkowitz, 1999;Ismail et al, 2006;Klauda et al, 2007;Chen and Smith, 2007;Yuet and Blankschtein, 2010).…”

Ammonium based stabilizers effectively counteract urea-induced denaturation in a small protein: insights from molecular dynamics simulations

“…We prefer SPC/E water model over SPC and TIP3P due to the better reproduction of bulk dynamics and structure by the former model. 75 The Duffy model, 76,77 consistent with the OPLS-AA force eld 68 has been adopted for urea. The OPLS force eld parameters for urea employed by various eminent groups for investigating a broad spectrum of research interest have been listed below.…”

Cloud droplet activation mechanisms of amino acid aerosol particles: insight from molecular dynamics simulations

“…MD simulations can thus serve as an important complement to experimental studies. Starting from the pioneer paper by Alejandre et al (1995), extensive MD simulations on surface tension have been carried out for planar liquidÁ gas interfaces (Yeh and Berkowitz, 1999;Ismail et al, 2006;Chen and Smith, 2007;Klauda et al, 2007;Yuet and Blankschtein, 2010). Meanwhile, MD studies on spherical liquidÁgas interfaces mimicking ambient droplet activation are increasing (Thompson et al, 1984;Zakharov et al, 1997;Van Giessen and Blokhuis, 2009;Li et al, 2010Li et al, , 2011Sampayo et al, 2010).…”