Dynamics of CO2 Scattering off a Perfluorinated Self-Assembled Monolayer. Influence of the Incident Collision Energy, Mass Effects, and Use of Different Surface Models
Dynamics of CO2 Scattering off a Perfluorinated Self-Assembled Monolayer. Influence of the Incident Collision Energy, Mass Effects, and Use of Different Surface Models
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DOI：
10.1021/jp809756f
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发表时间：
2009-04-23
影响因子：
2.9
通讯作者：
Martinez-Nunez, Emilio
中科院分区：
文献类型：
--
作者：
Nogueira, Juan J.;Vazquez, Saulo A.;Martinez-Nunez, Emilio
采用显式原子（EA）和联合原子（UA）模型代表金表面的全氟烷基硫醇自组装单层（F-SAM），通过经典轨迹计算研究了CO2与金表面F-SAM的碰撞动力学。CO2分子在1.6、4.7、7.7和10.6 kcal/mol的初始碰撞能量下垂直于表面。散射的CO2分子的旋转分布与实验确定的CO2与全氟聚醚的液体表面的碰撞分布一致。该协议特别适合EA模型。在单独的模拟中研究了质量在能量传递效率中的作用，其中F原子的质量被氢或氯的质量取代，同时保持势能函数不变。计算预测观察到的趋势，即较少的能量转移到表面的烷基链的质量增加。EA和UA模型获得的结果之间存在显着差异。与EA表面相比，UA表面导致能量传递效率的增强。其原因在于UA表面的较软结构，这有利于从平移到链间振动模式的转移。
The dynamics of collisions of CO2 with a perfluorinated alkanethiol self-assembled monolayer (F-SAM) on gold were investigated by classical trajectory calculations using explicit atom (EA) and united atom (UA) models to represent the F-SAM surface. The CO2 Molecule was directed perpendicularly to the surface at initial collision energies of 1.6, 4.7, 7.7, and 10.6 kcal/mol. Rotational distributions of the scattered CO2 molecules are in agreement with experimental distributions determined for collisions of CO2 with liquid surfaces of perfluoropolyether. The agreement is especially good for the EA model. The role of the mass in the efficiency of the energy transfer was investigated in separate simulations in which the mass of the F atoms was replaced by either that of hydrogen or chlorine, while keeping the potential energy function unchanged. The calculations predict the observed trend that less energy is transferred to the surface as the mass of the alkyl chains increases. Significant discrepancies were found between results obtained with the EA and UA models. The UA surface leads to an enhancement of the energy transfer efficiency in comparison with the EA surface. The reason for this is in the softer structure of the UA surface, which facilitates transfer from translation to interchain vibrational modes.