Tasić Uros, Alexeev Yuri, Vayner Grigoriy, Crawford T Daniel, Windus Theresa L, Hase William L
Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, USA.
Phys Chem Chem Phys. 2006 Oct 28;8(40):4678-84. doi: 10.1039/b609743j. Epub 2006 Sep 20.
Ab initio calculations at the CCSD(T)/aug-cc-pVTZ level of theory were used to characterize the Ar-CH(3)OH intermolecular potential energy surface (PES). Potential energy curves were calculated for four different Ar + CH(3)OH orientations and used to derive an analytic function for the intermolecular PES. A sum of Ar-C, Ar-O, Ar-H(C), and Ar-H(O) two-body potentials gives an excellent fit to these potential energy curves up to 100 kcal mol(-1), and adding an additional r(-n) term to the Buckingham two-body potential results in only a minor improvement in the fit. Three Ar-CH(3)OH van der Waals minima were found from the CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVTZ calculations. The structure of the global minimum is in overall good agreement with experiment (X.-C. Tan, L. Sun and R. L. Kuczkowski, J. Mol. Spectrosc., 1995, 171, 248). It is T-shaped with the hydroxyl H-atom syn with respect to Ar. Extrapolated to the complete basis set (CBS) limit, the global minimum has a well depth of 0.72 kcal mol(-1) with basis set superposition error (BSSE) correction. The aug-cc-pVTZ basis set gives a well depth only 0.10 kcal mol(-1) smaller than this value. The well depths of the other two minima are within 0.16 kcal mol(-1) of the global minimum. The analytic Ar-CH(3)OH intermolecular potential also identifies these three minima as the only van der Waals minima and the structures predicted by the analytic potential are similar to the ab initio structures. The analytic potential identifies the same global minimum and the predicted well depths for the minima are within 0.05 kcal mol(-1) of the ab initio values. Combining this Ar-CH(3)OH intermolecular potential with a potential for a OH-terminated alkylthiolate self-assembled monolayer surface (i.e., HO-SAM) provides a potential to model Ar + HO-SAM collisions.
在CCSD(T)/aug-cc-pVTZ理论水平下进行的从头算计算，用于表征Ar-CH(3)OH分子间势能面（PES）。针对四种不同的Ar + CH(3)OH取向计算了势能曲线，并用于推导分子间PES的解析函数。Ar-C、Ar-O、Ar-H(C)和Ar-H(O)二体势的总和对这些高达100 kcal mol(-1)的势能曲线给出了极佳的拟合，并且在Buckingham二体势中添加一个额外的r(-n)项只会使拟合有微小改进。通过CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVTZ计算发现了三个Ar-CH(3)OH范德华极小值。全局极小值的结构与实验总体上吻合良好（X.-C. Tan、L. Sun和R. L. Kuczkowski，《分子光谱学杂志》，1995年，第171卷，第248页）。它呈T形，羟基H原子相对于Ar是顺式的。外推到完全基组（CBS）极限，全局极小值在考虑基组叠加误差（BSSE）校正后的阱深为０.72 kcal mol(-1)。aug-cc-pVTZ基组给出的阱深仅比该值小0.10 kcal mol(-1)。另外两个极小值的阱深与全局极小值相差在0.16 kcal mol(-1)以内。解析的Ar-CH(3)OH分子间势也将这三个极小值确定为仅有的范德华极小值，并且解析势预测的结构与从头算结构相似。解析势确定了相同的全局极小值，并且极小值的预测阱深与从头算值相差在0.05 kcal mol(-1)以内。将这种Ar-CH(3)OH分子间势与OH端基烷基硫醇盐自组装单分子层表面（即HO-SAM）的势相结合，提供了一个对Ar + HO-SAM碰撞进行建模的势。
