【作者】 吴玲；

【导师】 杨忠志；

【作者基本信息】 辽宁师范大学 ， 物理化学， 2004， 硕士

【摘要】 偶极矩是表示分子中电荷分布情况的物理量,可以由分子的对称性推测分子有无偶极矩,也可由分子有无偶极矩及偶极矩的大小了解分子结构的信息。偶极矩沟通了分子的微观结构与宏观性能特征,所以进行化合物偶极矩的计算和研究,具有十分重要的理论意义和工程价值。而传统的从头计算所需要的计算量太大,这主要是由于利用从头算计算偶极矩要求用很大的基组,才能得到相对准确的结果,这样就要消耗大量的机时。因而有必要发展一种准确的、计算上易于实现的方法来探讨体系的结构和性质间的内在关系。我们以密度泛函理论和电负性均衡原理为基础,应用修正的电负性均衡方法(MEEM),利用最小二乘法,拟合确定了一些分子中各种类型原子的参数。运用这些参数,计算了一些分子的偶极矩,其结果可以和从头算相关,并可以说明一些化学规律。更多还原

【Abstract】 The calculation of dipole moment by MEEMThe dipole moment is a physical quantity, which can indicate the charge distribution of the molecule. The value of dipole moment can be conferred from the situation of the molecular symmetry, and vice versa. Since the dipole moment links up the microcosmic structure and the macroscopic performance characteristic, it is very important to calculate the dipole moment of molecules. While conventional ab initio methods is too time-consuming to afford, because the accurate prediction of dipole moments appears to be possible only with the utilization of significantly large basis sets, so we should develop an accurate and economic method to probe the relationship between structures and properties. We have proposed modified electronegativity equalization method (MEEM) based on density functional theory and electronegativity equalization principle. Using a separated program, through regression and least-squares optimization, the parameters of atoms in molecules are determined. By these parameters, the dipole moments of some molecules are calculated. The results show well agreement with those obtained by ab initio methods, and it can also account for some chemical rules.更多还原