CHEM01200604005 A. K. Pathak - Homi Bhabha National Institute

Table 2.1. Weighted average energy values for I 2•¯.nH 2 O clusters (n=1-8) at BHHLYP/6-311++G(d,p)
level of theory (for I atom split valence 6-311 basis set is used).
I 2 •− .nH 2 O #
Weighted average
Weighted average
Weighted average
solvation energy,
interaction energy,
vertical detachment
E w solv (kcal/mol)
E w
int
(kcal/mol)
energy, VDE w (eV)
n=1 (1) 10.69 10.88 4.51
n=2 (2) 20.33 20.37 4.92
n=3 (4) 32.43 24.52 5.03
n=4 (7) 46.9 27.7 5.14
n=5 (7) 56.43 34.87 5.45
n=6 (7) 64.33 40.6 5.66
n=7 (7) 77.31 43.77 5.77
n=8 (9) 89.97 45.47 5.85
# Values in the parentheses are the number of minimum energy structures for each size of clusters.
hydrated cluster followed by single point energy calculation at the same level of theory.
E
I2
.−
is also evaluated in the same way, i.e., by removing the water part of the optimized
structure followed by the single point energy calculation. Weighted average interaction
energy,
E w
int
is also calculated for all the hydrated clusters and the results are tabulated in
Table 2.1. The plot of
E w
int
vs. n is displayed in Fig. 2.5(b) showing the geometrical shell
closing at n=4 and n=8. The geometrical shell closing is due to the formation of
respective one and two H-bonded water tetramers surrounding the solute. Thus, though
the stabilzation energy profiles show a linear increment in energy with the successive
addition of solvent H 2 O units for I •− 2 .nH 2 O (n=1-8) clusters, the interaction energy
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