Zhu Hua, Guo Yong, Xue Ying, Xie Daiqian
Department of Chemistry, Sichuan University, Chengdu 610064, People's Republic of China.
J Comput Chem. 2006 Jul 15;27(9):1045-53. doi: 10.1002/jcc.20421.
An ab initio potential energy surface for the Ar--OCS dimer was calculated using the coupled-cluster singles and doubles with noniterative inclusion of connected triples [CCSD(T)] with a large basis set containing bond functions. The interaction energies were obtained by the supermolecular approach with the full counterpoise correction for the basis set superposition error. The CCSD(T) potential was found to have two minima corresponding to the T-shaped and the collinear Ar--SCO structures. The two-dimensional discrete variable representation method was employed to calculate the rovibrational energy levels for five isotopomers Ar--OCS, Ar--OC34S, Ar--O13CS, Ar--18OCS, and Ar--17OCS. The calculated pure rotational transition frequencies for the vibrational ground state of the five isotopomers are in good agreement with the observed values. The corresponding microwave spectra show that the b-type transitions (Delta Ka = +/-1) are significantly stronger than the a-type transitions (Delta Ka = 0). Minimum-energy structures of the Ar2--OCS trimer were been determined with MP2 optimization, whereas the minimum-energy structures of the Arn--OCS clusters with n = 3-14 were obtained with the pairwise additive potentials. It was found that there are two minima corresponding to one distorted tetrahedral structure and one planar structure for the ternary complex. The 14 nearest neighbor Ar atoms form the first solvation shell around the OCS molecule.
使用耦合簇单双激发并非迭代包含连接三激发[CCSD(T)]方法，结合包含键函数的大基组，计算了Ar--OCS二聚体的从头算势能面。通过超分子方法并对基组叠加误差进行完全抵消校正来获得相互作用能。发现CCSD(T)势能有两个最小值，分别对应T形和共线Ar--SCO结构。采用二维离散变量表示法计算了五种同位素异构体Ar--OCS、Ar--OC34S、Ar--O13CS、Ar--18OCS和Ar--17OCS的振转能级。计算得到的这五种同位素异构体振动基态的纯转动跃迁频率与观测值吻合良好。相应的微波光谱表明，b型跃迁（ΔKa = +/-1）明显强于a型跃迁（ΔKa = 0）。用MP2优化确定了Ar2--OCS三聚体的最低能量结构，而对于n = 3 - 14的Arn--OCS团簇，用成对加和势得到了最低能量结构。发现三元复合物有两个最小值，分别对应一种扭曲四面体结构和一种平面结构。14个最近邻的Ar原子在OCS分子周围形成了第一溶剂化层。
