Anatomy of bond formation. Bond length dependence of the extent of electron sharing in chemical bonds

This paper reports the application of an index, which we propose to call the shared-electron distribution index, for quantifying the changes to the extent of electron sharing during the making or breaking of chemical bonds. For this purpose we use this index, which is based on the correlated pair density, to monitor the effects of increasing the bond length in four representative diatomic molecules. We do of course employ wave functions which describe correctly the dissociation process. It is found for the nonpolar bonds in H2 and N2 that the degree of electron sharing increases monotonically with shortening of the bond length, but that there appears to be no molecule-specific significance to the location of the point of inflexion. The variation of the extent of electron sharing with internuclear distance is somewhat more complex for the polar bonds in LiH and BeH, but it reflects directly the known variation of the nature of the wave functions.