硝酸甲酯分子间相互作用的DFT和ab initio比较

Comparison of DFT with Ab initio Method on the Study of Intermolecular Interaction of (CH_3ONO_2)_2

用密度泛函理论(DFT)和从头算(abinitio)方法,分别在B3LYP/6-31G和HF/6-31G水平上求得硝酸甲酯三种二聚体的全优化几何构型和电子结构,并用6-311G和6-311++G基组进行总能量计算.对HF/6-31G计算结果进行MP4SDTQ电子相关校正.在各基组下均进行基组叠加误差(BSSE)和零点能(ZPE)校正求得结合能.对6-31G优化构型作振动分析并基于统计热力学求得200～600K温度下单体和二聚体的热力学性质.详细比较两种方法的相应计算结果,发现DFT求得的分子间距离较短,分子内键长较长,所得结合能均小于相应abinitio计算值.

The geometries and electronic structures of methyl nitrate and its dimers have been calculated by DFT method at the B3LYP/6-31G* level and ab initio method at the HF/6-31G* level respectively. The total energies using 6-311G** and 6-311++G** basis sets have been calculated. Dimer binding energies at the HF/6-31G* level have been corrected for MP4SDTQ electron correlation. All the binding energies have been corrected by the basis set superposition error (BSSE) and zero point energies (ZPE). Based on the vibrational analysis, the changes of thermodynamic properties at 200 similar to 600 K temperatures from mono to dimer have been calculated using the statistical-thermodynamic method. It is found that DFT method gives shorter intermolecular distances in a dimer, larger bond lengths in a molecule, and much smaller binding energies than those given by ab initio method.