氘代甲烷几何构型及物性的量子化学研究

Geometric Configuration and Properties of Methane Series

用HF/6 31G 、密度泛函方法B3LYP/31G 、二级微扰MP2/6 31G 、四级微扰MP4/6 31G 方法对甲烷和氘代甲烷进行几何构型全优化,并将优化的结果与实验值进行比较.用上述4种方法对甲烷和氘代甲烷分子进行分子的振动基频计算.密度泛函、二级微扰、四级微扰优于HF/6 31G ,尤其是密度泛函、四级微扰方法.密度泛函方法所用的机时远小于微扰方法.不同方法计算所得的氘代甲烷振动频率值与实验值的最大误差为10 4%,最小误差为2 0%.

Ab initio restricted HatreeFock(RHF) calculations, MollerPlesset correction calculations of the correlation energy, and the density functional theoretical calculations using B3' exchange and LeeYangParr's correlation functional(B3LYP) with 631G basic set are compared by optimizing the equilibrium structure of CD4 and CH4 and studying their fundamental vibration frequencies. The results are better than HF's, which are obtained by MP2, DFT, MP4 methods. But MP4 method needs too much CPU time. B3LYP is the best choice. The range of relative errors is from 20% to 104% between the calculated fundamental vibration frequencies and the observed ones.