Surface segregation in a binary mixture of ionic liquids: Comparison between high-resolution RBS measurements and molecular dynamics simulations

K Nakajima and S Nakanishi and Z Chval and M Lisal and K Kimura, JOURNAL OF CHEMICAL PHYSICS, 145, 184704 (2016).

DOI: 10.1063/1.4967260

Surface structure of equimolar mixture of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide (C(2)C(1)ImTf2N) and 1-ethyl-3-methylimidazolium tetrafluoroborate (C(2)C(1)ImBF4) is studied using high-resolution Rutherford backscattering spectroscopy (HRBS) and molecular dynamics (MD) simulations. Both HRBS and MD simulations show enrichment of Tf2N in the first molecular layer although the degree of enrichment observed by HRBS is more pronounced than that predicted by the MD simulation. In the subsurface region, MD simulation shows a small depletion of Tf2N while HRBS shows a small enrichment here. This discrepancy is partially attributed to the artifact of the MD simulations. Since the number of each ion is fixed in a finite-size simulation box, surface enrichment of particular ion results in its artificial depletion in the subsurface region. Published by AIP Publishing.

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