电子相关和基组效应对丙氨酸量子化学参数的影响

摘要

Alanine has two most stable conformers such as conformer I and conformer II. The HF amd density functional methods have been employed to investigate electronic correlation and basis set (diffuse function and polarization function) effects on frontier orbitals energy gap (ELUMo --EHOMO), dipole moment (I.t), polarizability (or) and total energy of most stable conformers of alanine at 6--31G, 6--31G* , 6-- 3IG** , 6--31+G, 6--31++G, 6--31+G* , 6--31++G*, 6--31+G**, 6--31q-+O~ level. The calculated results show the quantum chemical parameters calculated by B3LYP and HF are remarkably dif- ferent. The dipole moment and total energy depend more The polarizability is influenced by more diffuse function tion gives rise to increase of frontier orbital energy gap, tier orbital energy gap. on polarization function than on diffuse function. than polarization function. The polarization rune- while diffuse function results in decrease of fron-%丙氨酸有两种最稳定的构象，分别为构象I（conformerI）和构象II（conformerII）．采用HF方法和密度泛函理论（DFT）方法，在6—31G、6—31G＊、63IG＊＊、6—3l＋G、6—31＋＋G、6—31十G＊、6—31＋＋G＊、6—31＋G～、6—31＋＋G～基组水平上，考察了电子相关和基组（包括弥散函数和极化函数）效应对丙氨酸两种最稳定结构的偶极矩、极化率、前线轨道能隙、和总能量的影响．计算结果表明方法不同，所得的量子化学参数明显不同．极化函数对偶极矩和总能量的影响大于弥散函数的影响．弥散函数对极化率的影响大于极化函数的影响．极化函数导致前线轨道能隙值增大，弥散函数导致前线轨道能隙值减小．