Division of Chemistry, Graduate School of Science, Hokkaido University, 060-0810 Sapporo, Japan.
J Phys Chem A. 2012 Oct 18;116(41):10172-81. doi: 10.1021/jp305965r. Epub 2012 Oct 4.
The structures of the simplest aromatic clusters, benzene clusters (C(6)H(6))(n), are not well elucidated. In the present study, benzene clusters (C(6)H(6))(n) (n ≤ 30) were investigated with the all-atom optimized parameters for liquid simulation (OPLS) potential. The global minima and low-lying minima of the benzene clusters were searched with the heuristic method combined with geometrical perturbations. The structural features and growth sequence of the clusters were examined by carrying out local structure analyses and structural similarity evaluation with rotational constants. Because of the anisotropic interaction between the benzene molecules, the local structures consisting of 13 molecules are considerably deviated from regular icosahedron, and the geometries of some of the clusters are inconsistent with the shapes constructed by the interior molecules. The distribution of the angle between the lines normal to two neighboring benzene rings is anisotropic in the clusters, whereas that in the liquid benzene is nearly isotropic. The geometries and energies of the low-lying configurations and the saddle points between them suggest that most of the configurations previously detected in supersonic expansions take different orientations for one to four neighboring molecules.
最简单的芳香族团簇（苯团簇（C(6)H(6))(n)）的结构尚未得到很好的阐明。在本研究中，使用全原子优化参数用于液体模拟（OPLS）势对苯团簇（C(6)H(6))(n)（n ≤ 30）进行了研究。通过启发式方法与几何变形相结合，搜索了苯团簇的全局最小和低能最小。通过进行局部结构分析和旋转常数的结构相似性评估，考察了团簇的结构特征和生长顺序。由于苯分子之间的各向异性相互作用，由 13 个分子组成的局部结构明显偏离于规则的二十面体，并且一些团簇的几何形状与由内部分子构造的形状不一致。在团簇中，垂直于两个相邻苯环的直线之间的角度分布是各向异性的，而在液态苯中几乎是各向同性的。低能构型和它们之间鞍点的几何形状和能量表明，以前在超声速膨胀中检测到的大多数构型对于一到四个相邻分子采取了不同的取向。
