On bond orders and valences in the <i>Ab initio</i> quantum chemical theory

Abstract

Abstract The concept of bond order and valence indices calculated at the ab initio level is discussed in connection with their close relationship to the nonclassical exchange effects in bonding. An improved definition of bond order and free valence indices is given for the open‐shell SCF ( UHF ) case, and the generalization of the bond order and valence indices to correlated wave functions is also introduced.