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Atomisticmolecular dynamics simulations of small clusters andnanodroplets of the ionic liquid 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide[EMIM-Tf2N] subject to an external electric field wereperformed. A 125-ion-pair droplet was found to be nearly sphericalwith an isotropic distribution of cations and anions under vacuumconditions. The droplet was subjected to external electric fieldsof varying strength, and ion emission events were observed. The initiallyspherical droplet is elongated along the electric field axis, resultingin nonspherical behavior and increased net dipole values after theapplication of strong electric fields. The critical electric fieldrequired for ion field emission was determined to be 0.985 V/nm, inagreement with the experimental value of 1.0 V/nm. Excellent agreementis found in the prediction of ionic emission products for a neutral125-ion-pair droplet of the ionic liquid at an electric field strengthof 1.2 V/nm when compared to the results of two independent experiments.Small ionic liquid clusters were investigated with respect to theirthermal stabilities and were found to be thermally stable well aboveroom temperature. The role of electric fields in the dissociationof small charged ion clusters was also investigated. [ABSTRACT FROM AUTHOR]

Abstract: The selective hydrogenation of acetylene in the presence of ethylene over Pd catalysts (generally modified with silver) is of critical importance to prevent deactivation of polyethylene polymerization catalysts. In this study, density functional theory has been used to investigate the diffusion of carbon and hydrogen into the subsurface region of Pd(111), and subsequently, to explore the effects of these subsurface species on the selective acetylene hydrogenation reaction on Pd(111). In addition, the influence of subsurface Ag on the thermodynamics and kinetics of C2H2 hydrogenation has been examined. We find that the presence of subsurface H lowers the barriers for each C2H X hydrogenation step, and could increase the overall activity of the hydrogenation reaction with a corresponding decrease in the selectivity towards ethylene. In contrast, modification with subsurface C or Ag appears to lead to heightened barriers for ethylene hydrogenation, and may increase the selectivity of the Pd(111) catalyst. [Copyright &y& Elsevier]