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基于电负性均衡方法(EEM),依据原子类型和成键对原子进行细致划分,以准确计算分子中的原子电荷。为准确计算分子中原子的电荷,构建了包含214个分子、含各类不同基团的训练集,采用B3LYP/6-31g~*基组对分子进行优化并得到各个分子中的原子Mulliken电荷。与其他校正方法将同一类原子视为拥有相同的有效电负性和有效硬度值不同,本文在EEM方程中,依据成键类型和化学环境变化,将C、N、O分别分为为4种、3种和2种不同类型,相应采用不同的电负性和硬度价态标度值,并采用全局优化算法对训练集进行优化以得到各类原子的EEM参数值。本文讨论了这些参数与其他方法所得到的参数的差异,并讨论了本方法与其他校正方法的区别。利用本文校正所得EEM方程参数,对不在训练集中的几个杂环分子的EEM电荷进行了计算,取得了较为满意的结果。
Based on the electronegativity equalization method (EEM), atoms are finely divided according to atomic type and bonding to accurately calculate the atomic charge in the molecule. In order to accurately calculate the charge of atoms in a molecule, a training set containing 214 molecules with different groups was constructed. The B3LYP / 6-31g ~ * basis set was used to optimize the molecules and obtain the Mulliken charge of each molecule. Different from other calibration methods, the same type of atom is considered to have the same effective negative electromagnetism and effective hardness. In this paper, CEM, N and O are divided into four types according to the type of bonding and chemical environment, respectively , Three kinds and two kinds of different types. Different electronegativity and hardness valence scale values are correspondingly adopted, and the global optimization algorithm is used to optimize the training set to obtain the EEM parameter values of all kinds of atoms. This article discusses the differences between these parameters and those obtained by other methods and discusses the differences between this method and other correction methods. Using the parameters of the EEM equation corrected in this paper, the EEM charges of several heterocyclic molecules that are not in the training set are calculated, and the satisfactory results are obtained.