丙酮酸分子结构与振动光谱的密度泛函理论研究

用密度泛函方法BLYP、B3LYP和从头算Hartree-Fock(HF)方法在6-31G*基组水平上对丙酮酸分子的几何结构（甲基的重叠式和交错式两种构象）和振动光谱分别进行了优化和计算，并给出了各种频率所对应的红外强度及拉曼活性，对光谱进行了指认。结果表明：在丙酮酸分子的两种构象中，重叠式比较稳定*B3LYP计算得到的构型参数与实验结果比较一致；在振动频率的计算中，BLYP未标度力场所计算的非CH3伸缩振动基频预测值和实验值的平均绝对偏差为10.4cm-1；而HF标度力场的平均绝对偏差为17.9cm-1。说明两者的结果与实验观测频率比较吻合，但B3LYP的频率计算值偏差（38.3cm-1）较大。根据振动频率的势能分布和红外光谱强度对此分子的振动基频进行了理论归属。

Structures and Vibrational Frequencies of Pyruvic Acid:Density Functional Theory Study

Density functional theory BLYP(using Beckes and Lee-Yang-Parr’s correlation functionals),ab initio Hartree-Fock(HF)and hybrid DFT/HF B3LYP calculations were carried out to study the structure and vibrational spectra of pyruvic acid.Molecular conformation calculations were made for two possible conformers(eclipsed and staggered with respect to the methyl group)of the compound Calculated results show that:the stable conformer of pyruvic acid is the eclipsed one;The BLYP/6-31G* and scaled HF/6-31G* frequencies correspond well with each other and with available experimental assignment of the normal vibrational modes.On the basis of the comparison between calculated and experimental results,assignments of fundamental vibrational modes are examined.