用量子化学CCSD(T)/aug-cc-pVTZ方法与基组,计算了van de Waals复合物NaNe和NaAr复合物基态的相互作用势,并进行了基组重叠误差校正。采用Murrell-Sorbie函数进行非线性最小二乘法拟合,得到了NaX(X=Ne、Ar)复合物的势能函数解析表达式,确定了NaX(X=Ne、Ar)复合物的平衡结构和离解能,并进一步计算了这些复合物的光谱常数。
The interacting patterns and mechanism of the catechin and thymine have been investigated with the density functional theory Becke＇s three-parameter nonlocal exchange functional and the Lee, Yang, and Parr nonlocal correlation functional （B3LYP） method by 6-31＋G＊ basis set. Thirteen stable structures for the catechin-thymine complexes have been found which form two hydrogen bonds at least. The vibrational frequencies are also studied at the same level to analyze these complexes. The results indicated that catechin interacted with thynfine by three different hydrogen bonds as N-H…O, C-H…O, O-H…O and the complexes are mainly stabilized by the hydrogen bonding interactions. Theories of atoms in molecules and natural bond orbital have been adopted to investigate the hydrogen bonds involved in all systems. The interaction energies of all complexes have been corrected for basis set superposition error, which are from -18.15 k J/mol to -32.99 kJ/mol. The results showed that the hydrogen bonding contribute to the interaction energies dominantly. The corresponding bonds stretching motions in all complexes are red-shifted relative to that of the inonomer, which is in agreement with experimental results.
运用密度泛函理论在B3LYP/6-31++G**理论水平研究N,N-二甲基脲二聚体和三聚体氢键结构.构型优化和频率计算得到3个稳定的二聚体和三聚体氢键异构体.经基组重叠误差和零点振动能校正后,最稳定的二聚体和三聚体的相互作用能分别为-48.52和-72.15 kJ/mol.振动分析表明二聚体和三聚体存在典型的红移氢键.热力学分析显示,298.15 K和标准压力下,二聚体和三聚体的形成是一个放热过程.Abstract：The hydrogen bonding structures of the N,N-Dimethylurea dimer and trimer have been investigated using density functional theory at B3LYP/6-31++G** level. Three stable structures of the dimer and trimer have been obtained by the optimized geometries and frequencies calculation. After basis set superposition error and zero-point vibration energy correction, it is found that the most stable dimer and trimer have strong hydrogen bonding interaction with -48.52 and -72.15 kJ/mol. Vibration analysis show that dimer and trimer have typical red-shift hydrogen bond. In addition, thermal stability indicates that the formation of dimer and trimer at 298.15K and standard pressure is a exothermic process.
