The surface structure of ionic liquids: comparing simulations with X-ray measurements

Sloutskin, E. ; Lynden-Bell, R. M. ; Balasubramanian, S. ; Deutsch, M. (2006) The surface structure of ionic liquids: comparing simulations with X-ray measurements Journal of Chemical Physics, 125 (17). pp. 4715-174721. ISSN 0021-9606

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Official URL: http://jcp.aip.org/resource/1/jcpsa6/v125/i17/p174...

Related URL: http://dx.doi.org/10.1063/1.2361289

Abstract

The surface-normal electron density profile of an ionic liquid, [bmim][PF6], derived from x-ray reflectivity measurements, is compared with two independent molecular-dynamics simulations. It is shown that a meaningful comparison requires a detailed accounting for both thermal and nonthermal surface roughening effects. The former is due to thermally excited capillary waves, and the latter is due to the molecular zero-point motion and form. These quantities influence very significantly, but differently, the simulated and measured density profiles. Stripping off these effects from both types of profiles yields the intrinsic structure factor of the surface. The simulated intrinsic structure factors are found to deviate considerably from the measured one. The introduction of additional ad hoc surface roughness to the simulated profiles greatly reduces the deviation, however, no physical origin for this effect can be identified. The method employed in this study should prove useful for simulation-experiment comparisons of other liquid surfaces, provided they obey capillary-wave theory, as do almost all liquid surfaces studied to date by x-ray reflectivity.

Item Type:Article
Source:Copyright of this article belongs to American Institute of Physics.
Keywords:Organic Compounds; Surface Structure; Liquid Structure; Molecular Dynamics Method; X-ray Reflection; Surface Roughness; Capillary Waves
ID Code:79838
Deposited On:30 Jan 2012 04:49
Last Modified:30 Jan 2012 04:49

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