Free-Energy Profile of Small Solute Molecules at the Free Surfaces of Water and Ice, as Determined by Cavity Insertion Widom Calculations

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• 作者：Lí ; via B. Pá ; rtay ; Pá ; l Jedlovszky ; Paul N. M. Hoang ; Sylvain Picaud ; Mihaly Mezei
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：July 5, 2007
• 年：2007
• 卷：111
• 期：26
• 页码：9407 - 9416
• 全文大小：620K
• 年卷期：v.111,no.26(July 5, 2007)
• ISSN：1932-7455

文摘

The solvation free-energy profiles of 15 different small solutes (i.e., Ar, HF, H₂O, H₂S, NH₃, CH₄, CH₂F₂,CH₂Cl₂, CHCl₃, methanol, formaldehyde, formic acid, CO₂, acetone, and acetonitrile) have been calculatedacross the water/vapor and ice/vapor interfaces by means of Monte Carlo simulations and cavity insertionWidom (CIW) calculations. The CIW calculations have been performed using a new, efficiently parallelizedalgorithm, which can provide linear speedup on a large number of processors in a distributed memory system.All the solutes considered show preference for being adsorbed at the surface of both liquid water and ice.The free-energy gain of this adsorption relative to the isolated state of the solute molecule is found to beindependent of the state (i.e., liquid versus frozen) of the condensed phase, and it is larger for solutes that areable to form stronger or more hydrogen bonds with the water molecules at the surface. On the other hand, thefree-energy gain of the adsorption from the bulk liquid phase is found to be stronger for solutes exhibitingstronger amphiphilic character. The solvation free energy of all the solutes studied is found to be considerablyhigher in ice than in bulk liquid water. The results obtained have several implications on the chemistry of theatmosphere, which are also discussed in the paper.