Department of Chemistry, School of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, Jiangsu 215123, People's Republic of China.
J Comput Chem. 2013 Mar 30;34(8):673-80. doi: 10.1002/jcc.23179. Epub 2012 Nov 23.
The intermolecular potential energy surface (PES) of argon with ethane has been studied by ab initio calculations at the levels of second-order Møller-Plesset perturbation (MP2) theory and coupled-cluster theory with single, double, and noniterative triple configurations (CCSD(T)) using a series of augmented correlation-consistent basis sets. Two sets of bond functions, bf1 (3s3p2d) and bf2 (6s6p4d2f), have been added to the basis sets to show a dramatic and systematic improvement in the convergence of the entire PES. The PES of Ar-ethane is characterized by a global minimum at a near T-shaped configuration with a well depth of 0.611 kcal mol(-1), a second minimum at a collinear configuration with a well depth of 0.456 kcal mol(-1), and a saddle point connecting the two minima. It is shown that an augmented correlation-consistent basis set with a set of bond functions, either bf1 or bf2, can effectively produce results equivalent to the next larger augmented correlation-consistent basis set, that is, aug-cc-pVDZ-bf1 ≈ aug-cc-pVTZ, aug-cc-pVTZ-bf1 ≈ aug-cc-pVQZ. Very importantly, the use of bond functions improves the PES globally, resulting accurate potential anisotropy. Finally, MP2 method is inadequate for accurate calculations, because it gives a potentially overestimated well depth and, more seriously, a poor potential anisotropy.
氩与乙烷的分子间势能面（PES）已通过从头算在二级 Møller-Plesset 微扰（MP2）理论和单、双和非迭代三配置（CCSD(T)）耦合簇理论水平上进行了研究，使用了一系列扩充相关一致基组。两套键函数 bf1（3s3p2d）和 bf2（6s6p4d2f）被添加到基组中，以显著且系统地提高整个 PES 的收敛性。Ar-乙烷的 PES 以近乎 T 形构型的全局最小值为特征，其势阱深度为 0.611 kcal mol(-1)，在共线构型中有第二个最小值，其势阱深度为 0.456 kcal mol(-1)，还有一个鞍点连接两个最小值。结果表明，一套键函数的扩充相关一致基组（无论是 bf1 还是 bf2）都可以有效地产生与下一个更大的扩充相关一致基组等效的结果，即 aug-cc-pVDZ-bf1 ≈ aug-cc-pVTZ，aug-cc-pVTZ-bf1 ≈ aug-cc-pVQZ。非常重要的是，键函数的使用全局改善了 PES，从而产生了准确的势能各向异性。最后，MP2 方法对于准确计算是不足的，因为它给出了潜在的高估势阱深度，更严重的是，给出了较差的势能各向异性。
