CHEM01200604005 A. K. Pathak - Homi Bhabha National Institute
CHEM01200604005 A. K. Pathak - Homi Bhabha National Institute
CHEM01200604005 A. K. Pathak - Homi Bhabha National Institute
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Cl<br />
Cl Br Br I I<br />
VIIIA VIIIB VIIIC<br />
Fig. 4.1. The fully optimized most stable structures calculated applying BHHLYP functional with 6-<br />
311++G(d,p) set of split valence basis function (6-311 basis set is used for iodine) for (IA) Cl 2 .H 2 O; (IB)<br />
Br 2 .H 2 O, (IC) I 2 .H 2 O; (IIA) Cl 2 .2H 2 O; (IIB) Br 2 .2H 2 O (IIC) I 2 .2H 2 O; (IIIA) Cl 2 .3H 2 O; (IIIB) Br 2 .3H 2 O,<br />
(IIIC) I 2 .3H 2 O; (IVA) Cl 2 .4H 2 O; (IVB) Br 2 .4H 2 O, (IVC) I 2 .4H 2 O; (VA) Cl 2 .5H 2 O; (VB) Br 2 .5H 2 O, (VC)<br />
I 2 .5H 2 O; (VIA) Cl 2 .6H 2 O; (VIB) Br 2 .6H 2 O, (VIC) I 2 .6H 2 O; (VIIA) Cl 2 .7H 2 O; (VIIB) Br 2 .7H 2 O, (VIIC)<br />
I 2 .7H 2 O; (VIIIA) Cl 2 .8H 2 O, (VIIIB) Br 2 .8H 2 O and (VIIIC) I 2 .8H 2 O. Cl, Br and I atoms are shown by<br />
marked spheres, the smallest ‘white’ colour spheres refer to H atoms and the rest (red colour) corresponds<br />
to O atoms in each structure.<br />
The structures of all these systems are widely different for the larger size clusters<br />
(n>6) though they are fairly similar in case of smaller clusters (n=1-6) except for n=2.<br />
The structure of Br 2 .nH 2 O (n=7) cluster is quite different from that in the earlier reported<br />
work at a lower level of theory. 55<br />
4.3.2. Atomic Charge and Bond Order<br />
The calculated Mulliken atomic charges over two Br atoms in Br 2 .H 2 O cluster are<br />
about +0.04 and -0.08 a.u. A small variation of atomic charge over two Br atoms is<br />
observed for different size hydrated clusters, Br 2 .nH 2 O, and observed to be in the range<br />
of 0.04–0.14 a.u. This suggests that Br 2 exists as a charge-separated ion-pair species<br />
76