叠氮甲烷二聚体分子间相互作用的abinitio研究

Ab Initio Study on the Intermolecular Interaction of Methyl Azide Dimers

运用abinitio方法 ,在HF水平 6 3 11G 基组下求得叠氮甲烷二聚体势能面上六种优化构型和电子结构。经MP2电子相关和基组叠加误差 (BSSE)以及零点能 (ZPE)校正 ,求得分子间相互作用能 ;结合能 ( 9.49kJ·mol-1)最大的二聚体为存在两个CHN氢键的六元环构型 ,属于D2h群。探讨了甲基内旋转对相互作用能的影响。由自然键轨道 (NBO)分析揭示了相互作用的本质。对单体和六种二聚体优化构型进行简谐振动分析 ,研究了IR光谱变化规律。此外还基于统计热力学求得 2 73 .15～ 80 0 .0 0K温度范围从单体形成二聚体的热力学性质变化。

Geometries and electronic structures of methyl azide and its dimers have been calculated firstly by using ab initio method at the HF level with the 6 311G ** basis set. The intermolecular interaction energy is calculated with MP2 electron correlation correction, basis set superposition error (BSSE) correction and zero point energy (ZPE) correction. The most stable dimer (the binding energy of 9.49 kJ·mol -1 ) possesses a six membered ring with two  CHN  hydrogen bonds and belongs to D 2h group. The effect of methyl internal rotation on the interaction energy is investigated. Natural bond orbital (NBO) analysis is performed to reveal the origin of the interaction. The harmonic vibrational analysis is used to study the optimized structure of the monomer and six dimers, and IR spectrum shifts are discussed. Based on the statistical thermodynamic method, the changes of thermodynamic properties from the monomer to dimer with the temperature ranging from 273.15 K to 800.00 K have been obtained.