中文摘要：

采用量子化学ONIOM（B3LYP/6-31＋＋G（d,p）：UFF）方法研究限域在扶手椅型单壁硼氮纳米管[（SWBNNT（5,5）、SWBNNT（6,6）和SWBNNT（7,7）]内,α-Ala的结构和手性转变机制.分子结构分析表明：与单体α-Ala相比,受限于SWBNNT（5,5）内的α-Ala分子沿纳米管轴向被拉伸,骨架C-C-C键角和C-C-N-C二面角明显增大,其他结构参数略有变化;受限于SWBNNT（（6,6）、（7,7））内的α-Ala结构变化愈来愈不明显.手性转变反应势能面计算结果表明：与单体α-Ala相比较,α-Ala在SWBNNT（（5,5）、（6,6）、（7,7））内时,羧基内氢转移和氢从手性碳转移至羰基的能垒,随纳米管管径的降低而降低.手性转变反应路径研究发现：α-Ala在不同直径的SWBNNT（（5,5）、（6,6）、（7,7））内时,完成手性转变所经历的反应路径条数以及过渡态和中间体的个数不同,体现了扶手椅型SWBNNT尺寸的变化对α-Ala手性转变反应通道的影响.

英文摘要：

The molecular structure and chiral shift mechanism ofα-alanine confined in single-walled armchair SWBNNT（5,5）,SWBNNT（6,6）and SWBNNT（7,7）were investigated by using the combined method of quantum chemistry ONIOM（B3LYP/6-31＋＋G（d,p）：UFF）.The research on the molecular structure shows that,compared with the case of monomerα-Ala,α-Ala molecule inside SWBNNT（5,5）is stretched along the nanotube axis.In addition,the bond angle of C-C-C and dihedral angle of C-C-N-C significantly increase and other structural parameters change slightly.The structural changes ofα-Ala confined in SWBNNT（（6,6）,（7,7））are increasing obscure.The calculation of potential energy surface in chiral shift reaction shows that：whenα-alanine is limited in BNNT of small diameter,the energy barriers of chiral transition ofα-alanine decrease with the decreasing diameter of carbon nanotubes,especially for the energy barriers of hydrogen transfer in hydrogen.The research to reaction channel of chiral shift shows that：Whenα-alanines are limited in single-walled armchair BNNT（5,5）,BNNT（6,6）and BNNT（7,7）of different diameters,there are different numbers of reaction paths,transient states and midbodies during the transition process,which reflects the confined effects of dimension of single-walled boron nitride nanotube on chiral transition ofα-alanine molecules.