NH_3(H_2O)_3氢键团簇的理论计算研究

Theoretical Calculation for Hydrogen Bonding Clusters of NH_3(H_2O)_3

用经验势与abinitio理论相结合的方法寻找了团簇NH3（H2O）3的稳定结构。对由经验势计算所得的100个初始结构，进一步用HF和MP2的理论方法，在6—31＋G（d，p）和6-311＋＋G（d，p）基组水平上对其进行几何优化、能量计算和频率计算。分析了氢键的特征以及团簇的结合能，并得到团簇的5种能量较低的稳定结构。计算结果表明：不同情况的氢键分布能够产生多个能量相近、空间结构不同的异构体；团簇中最稳定的异构体呈平面环状结构，分子间氢键键长在1．772～2．030A之间。

Stabilized structures of cluster were identified by ab initio theory and experiential potential method.One hundred configurations obtained by experiential potential calculation were refined using standard geometry optimizations at the HF and MP2 levels with the 6-31+G(d,p) and 6-311++G(d,p)basis set,and energies and frequency calculation were performed at the HF and MP2 levels with the same basis set.Hydrogen bond characteristic and bonding energies were analyzed,and five low-lying energy structures were obtained in the end.The results indicate that different distributions of the hydrogen bond will generate many different isomers with similar energy and different spatial configuration,the most stable isomer of clusters has a planar ring structure,molecular hydrogen bonds are between 1.772～2.030■.