Evaluation of molecular mechanics calculated binding energies for isolated and monolayer organic molecules on graphite

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• 作者：Thomas R. Rybolt ; Christina E. Wells ; Charles R. Sisson ; Claire B. Black ; Katherine A. Ziegler
• 关键词：Adsorption ; carbon ; on ; Gas– ; solid interaction energy ; Molecular mechanics ; Binding energy ; Adsorption energy ; Adsorption ; graphite ; on ; Thermal desorption
• 刊名：Journal of Colloid and Interface Science
• 出版年：2007
• 出版时间：15 October 2007
• 年：2007
• 卷：314
• 期：2
• 页码：434-445
• 全文大小：326 K

文摘

The calculated molecule–surface binding energy, X8MTB-3&_mathId=mml41&_user=10&_cdi=6857&_rdoc=13&_acct=C000050221&_version=1&_userid=10&md5=708797505f8dca91862e2ff6d0933696"">, for physical adsorption was determined using molecular mechanics MM2 parameters for a model graphite surface and various organic molecules. The results for were compared to published experimental binding energy values, E^*, from gas chromatography (GC) or thermal desorption (TD). The binding energies from GC were for isolated molecules in the Henry's law region of adsorption, and the binding energies from TD were for molecules in monolayer coverage on a highly oriented pyrolytic graphite (HOPG). A simple desorption model was used to allow the calculation of monolayer coverage to include both molecule–surface and molecule–molecule interactions and then the results were compared to experimental values. For the 14 TD organic adsorbates (polyaromatic hydrocarbons, alcohols, benzene, substituted benzenes, methane, chloroalkanes, N,N-dimethylformamide, and C₆₀ Buckyball), the experimental versus calculated binding energies were 8d39e4af384c54ff4967d""> and r²=0.967. The GC E^* values were also well correlated by calculated dc341d047ca762d791b86d95""> values for a set of 11 benzene and methyl substituted benzenes and for another set of 10 alkanes and haloalkanes. The TD mechanics computation provides a useful comparison to the one for GC data since adsorbate–adsorbate interactions as well as adsorbate–surface must be considered.