乙醇-水分子团簇C_2H_5OH(H_2O)_n(n=1-9)稳定结构的量子化学研究

Quantum Chemistry Study on the Stable Structures of C_2H_5OH(H_2O)_n (n=1-9) Clusters

采用密度泛函理论B3LYP方法,在B3LYP/6-311++G(2d,2p)//B3LYP/6-311++G(d,p)基组水平上对乙醇-水分子团簇(C2H5OH(H2O)n(n=1-9))的各种性质进行研究,如:优化的几何构型、结构参数、氢键、结合能、平均氢键强度、自然键轨道(NBO)电荷分布、团簇的生长规律等.结果表明,从二维(2-D)环状结构到三维(3-D)笼状结构的过渡出现在n=5的乙醇-水分子团簇中.此外,利用团簇结合能的二阶差分、形成能、能隙等性质,发现在n=6时乙醇-水分子团簇的最低能量结构稳定性较好,可能为幻数结构.最后,为了进一步探讨氢键本质,将C2H5OH(H2O)n(n=2-9)最低能量结构的各种性质与纯水分子团簇(H2O)n(n=3-10)比较,结果表明前者与后者中的水分子之间氢键相似.

We studied C2H5OH（H2O）n （n=1-9） clusters using density functional theory （DFT） at the B3LYP/6-311＋＋G（2d,2p）//B3LYP/6-311＋＋G（d,p） level. We calculated the properties that characterize the C2H5OH （H2O）n （n=1-9） clusters and these include optimal structures, structural parameters, hydrogen bonds, binding energies, average hydrogen bond strength, natural bond orbital （NBO） charge distributions, and cluster growth rhythm, etc. The results show that the transition from two-dimensional （2-D） cyclic structure to three-dimensional （3-D） cage structure occurs at n=5. Moreover, the lowest energy structure of the C2H5OH（H2O）n （n=6） cluster is probably a magic number structure as determined by the properties of the second order difference of the binding energy, the formation energy, and the energy gap. Finally, to probe the nature of the hydrogen bond, the properties of the lowest energy structures for the C2H5OH（H2O）n （n=2-9） clusters were compared with those of pure water clusters （H2O）n （n=3-10）, and our results show that the hydrogen bonds that form between water molecules in the former are similar to those in the latter.