计算化学在分子轨道教学中的应用

分子轨道理论是理解分子电子结构与微观性质的重要理论之一,也是本科生与研究生结构化学教学中的重点与难点。学生对原子轨道组合形成分子轨道、分子轨道能级交叉混合等知识的理解缺乏形象直观、定量的认识。本文通过基于量子化学或密度泛函理论的Gaussian 03计算软件,计算、绘制并分析了F_2、O_2、N_2、HF、CO等的分子轨道能级图,将学生较难理解的内容定量、直观地呈现出来,形象地解释了分子轨道成键原则与电子填充原则等分子轨道理论中的重难点,加深了学生对分子轨道理论的理解,特别是sp轨道混杂导致的σ_(2p_z)与π_(2p)轨道能级交叉这一难点,激发了学生学习的主动性和积极性,提高了教学质量。在此基础上,利用分子轨道理论分析了CO_2的电子结构,使学生学会应用分子轨道理论解决实际问题,巩固了相关课堂理论知识。

Application of Computational Chemistry into the Teaching of Molecular Orbital Theory

Molecular orbital (MO) theory is one of the most important theories to understand the electronic structure and microscopic properties, and it is also the key and difficult point in the teaching of inorganic chemistry and theoretical chemistry for undergraduate and graduate students. Since there is lack of the intuitive and quantitative diagrams for the formation of molecular orbitals from the atomic orbitals, as well as thes-p orbital mixing and the energy level crossing in the present textbook, students have difficulty in understanding the MO theory. In this paper, we introduce the computational chemistry into the teaching of the MO theory. Based on the theoretical results calculated by Gaussian 03 program, the images and energy levels of molecular orbitals for F₂, O₂, N₂, HF and CO are obtained and analyzed, which makes the abstract theory quantitative, intuitive, and easily to understand. Correspondingly, the rules of molecular orbital bonding and electron filling are well explained, which helps students to better understand the MO theory, especially for the s-p orbital mixing and the energy level crossing of σ_2pz and π_2p orbitals. According to the molecular orbital analysis of F₂, O₂, N₂, HF and CO, the electronic configuration of CO₂ is analyzed by using MO theory. On the basis of the teaching practice above, the students' initiativity and enthusiasm are greatly improved, and the effective learning of MO theory is realized.