中文摘要：

使用基于密度泛函理论的B3LYP方法，采用6-31＋g（d，P）基组，用Gaussian03对孤立条件下的手性α-丙氨酸分子结构特性进行理论计算．首先优化了三种α-丙氨酸分子的可能构型，进行了红外振动频率计算，由此得到三种稳定构型，而后由能量最低原理确定了α-丙氨酸分子最可能的构型．再由手性分子的空间结构特点，得到其对映体的结构，并进行了结构优化．最后在B3LYP／6—31＋g（d，P）水平上，对α-丙氨酸分子的一对对映体进行了VCD谱与前线分子轨道的计算与研究．

英文摘要：

In this paper,we theoretically calculated the structural characteristics of chiral Alpha Alanine under isolated condition using the B3LYP method based on density functional theory with the 6-31 ＋ g （d,p） basis set and Gaussian03. First, three kind of possible configurations of alpha alanine molecular was optimized, then we obtained three stable configuration by calculating the infrared vibration frequency. Then we ascertained the most likely configuration of alpha alanine molecules through the principle of the lowest energy. And we got the structure of it＇s enantiomers by the space structure characteristics of chiral molecular, carried out the optimization structure. Finally calculated VCD spectrum and the molecular frontier orbital on B3LYP/6-31 ＋ g（d,p） level.