Configuration interaction in valence bond theory

Configuration interaction tenichque is applied to the valence bond theory. Virtual VB orbitals are built, which are localized and orthogonal to their corresponding occupied orbitals and the excited VB structures are defined, which come from their corresponding fundamental VB structures. The testing calculations of H-2, LiH, HF show that the VB results using CI method match those of the molecular orbital based on the coupled cluster CCSD method, a nd the Cl technique may become a useful tool in VB method.