CHEM01200604005 A. K. Pathak - Homi Bhabha National Institute

Here, the symbols are used to denote intensity (I), frequency (ω), Plank constant (h )
inverse of Boltzmann constant multiplied by temperature (β ) 1/kT), time (t), and dipole
moment (μ).
3.3. Results and Discussion
The clusters, X. nH 2 O (X= Cl 2 •− , Br 2 •− , I 2 •− , CO 3 •− , NO 3
−
and CO 3 2− ) are
stabilized by the SHB, DHB and WHB interactions as discussed in Chapter 2. Due to
these interactions it is expected that bands due to O-H stretching and bending modes of
H 2 O in the hydrated clusters of X get shifted compared to that of free water molecule.
Based on the literature data on the stretching frequency of H 2 O (ν sym = 3657 cm -1 , ν asym =
3756 cm -1 ) and the present calculated values (ν sym = 3983 cm -1 , ν asym = 4087 cm -1 ) at
BHHLYP/6-311++G(d,p) level, the scaling factor is taken as 0.92 to account for the
anharmonic nature of vibration. At B3LYP level the scaling factor is found to be 0.96 to
account for the anharmonic nature of vibration.
H 2
O:IR
Intensity
0 1000 2000 3000 4000
Frequency (cm -1 )
Fig. 3.1. Calculated scaled IR spectra at BHHLYP/6-311++G(d,p) level free H 2 O molecule. The scaling
factor is taken as 0.92 to account for the anharmonic nature of stretching vibrations. Lorentzian line shape
has been applied with peak half-width of 10 cm -1 .
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