键能的分子轨道理论研究 1: 理论公式

从LCAO-MO出发, 给出了一个计算键能的近似方法, 即EAB(i)-∑∑CaiSabCbiεi为第i个占据分子轨道(MO)中的一对电子对A-B键键能的贡献。对所有分子轨道求和即为该键的键能: EAB=∑EAB(i)。按该方法, 不仅可以计算各种不同分子中每两个相键连原子间的键能, 还可以从MO及AO角度分析每一具体键, 如σ, π, δ键的键能以及各AO对键能的贡献。该方法虽有别于求键焓和平衡离解能De, 但计算结果和De的实验值甚相符合。通过对键能的分析研究, 能较好地揭示原子间的相互作用关系及化学键的强弱, 从而可进一步探讨化学反应活性, 反应速率等化学性质。

Molecular orbital theory studies on bond energy 1: Theoretic equation

A new way of calculating bond energy is proposed proceeding from LCAO-MO. On the basis of using the equation EAB(i)-∑∑CaiSabCbiεi as the contribution to the bond energy of A-B bond from a pair of electrons in the i occupied MO, it is easy to obtain the bond energy of A-B bond by summing up all MO, i.e., EAB=∑EAB(i). The bond energy between atoms linkaged each other in various molecules is calculated in this way, and the property of bond such as bond of σ, π or δ and the contribution of all AO for the bond energy is analysed at MO and AO views. Though this way is different from those in which the bond enthalpy and equilibrium dissociation energy De can be obtained, the results of calculation are well in accord with experiment values of De. By analysing the bond energy, the interacting relations between atoms and the strength of the chemical bond are well indicated and such chemical property as the chemical reactivity and reaction rate can be further probed.