where r1,S and r1,EQ are the electron density of the breaking bond
at a given reaction coordinate S on IRC path and at the reactant,
respectively; and r2,S and r2,EQ is the electron density of the
forming bond at a given reaction coordinate S on IRC path and at
the product, respectively. The value of B(r) changes along the
reaction coordinate S and can be used to determine the relative
variation trend between the breaking bond and the forming bond.
From the calculated results, the following facts may be deduced:
firstly, at the beginning and end of the reaction, the value of B(r)
should be 1.0. Secondly, when the value of B(r) increases along
the reaction coordinate S, the trend of the forming bond gains an
advantage over that of the breaking bond.We define the region as
‘forming bond region’. On the contrary, when the value of B(r)
decreases along the reaction coordinate S, the trend of the
breaking bond exceeds that of the forming bond. We define the
region as ‘breaking bond region’. Finally, Minimum and
Maximum values of B(r) indicate the relative variation trend
between the breaking bond and forming bond is in equilibrium.
We define the point as ‘equilibrium point’.