Do Your Own Valence Bond Calculation—A Practical Guide

This chapter provides the readers with know-how for performing VB calculations. The basic principles of GVB, VBSCF, BOVB and VBCI methods are briefly recalled, with all their available options, and exemplified with the calculation of the bond dissociation energy (BDE) for F 2 , chosen as being a well-known challenging case. The performances of the various VB methods are displayed and compared with those of molecular-orbital-based methods. Instructions follow for avoiding nonphysical results during BOVB calculations. Diabatic states are subsequently described (Tables 10.4 and 10.5) to quantify important concepts, such as resonance energy, covalency, and ionicity of a bond, and to generate VB diagrams (VBSCD and VBCMD). Inputs are provided for GVB and various levels of VBSCF and BOVB methods for calculating the BDE of F 2 . Other inputs show calculations of the Kekulé structures of benzene and its ground state. Finally, outputs for calculations of F 2 by BOVB and VBCISD are provided.