An Extended INDO-CI Theory of the General Relation between Bond Length and Bond Order

Abstract

Considering a system composed of even valence-shell electrons and formulating a CI calculation with inclusion of all the singly-excited and the simultaneous doubly-excited singlet configurations of the system, we extend our previous INDO theory of the relation between bond length and bond order for the ground-state singlet configuration. \cite{rf:1}It is thus shown that the previous relation for the ground-state singlet configuration can generally be applied to any singlet state by replacing every bond order of the ground-state singlet configuration with that of the ground or the excited singlet-state.It is also pointed out that bond orders of each singlet state can correctly be calculated by our projection-operator method.