CHEM01200604005 A. K. Pathak - Homi Bhabha National Institute

However, these calculations do not lead to any significant change in the structural
parameters of these hydrated clusters.
2.3.2. Solvent Stabilization and Interaction Energy
where E I
The stabilzation energy of I 2 •− .nH 2 O clusters can be expressed as
solv
E = E . − − ( nE E
I nH O HO+
. −),
. I
. −
2 2
. nH O
2 2 2 2
, E HO 2
and E
I2
.− refer to the total energy of the cluster I 2 •− .nH 2 O, the
energy of a single H 2 O molecule and the energy of the bare I 2 •− system, respectively.
Thus, E solv essentially refers to the total interaction energy of the solute with n solvent
H 2 O units around it in the hydrated cluster of size n. A number of minimum energy
configurations are obtained in these hydrated clusters and it is increasing with the size (n)
of the cluster. It is understood that at a particular temperature there will be a statistical
contribution of the conformers of a particular size to the overall property. So the
weighted average solvent stabilization energy ( E w
solv
) values are calculated and provided
in Table 1. The plot for the variation of E w
solv
vs. n is shown in Fig. 2.5(a). The weight
factor of a conformer within a particular size (n) of the cluster is calculated based on the
Boltzmann statistical population of the conformer at 150 K. It is observed that E w
solv
varies linearly with n, the number of water molecules in the hydrated clusters and the
variation of E w
solv
is best fitted as
E w
solv
= -0.83 + 11.25 n,
When, E w
solv
is expressed in kcal/mol and n is the number of water molecules. This linear
fitted plot has correlation coefficient ~ 0.999 promising the power of prediction of
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