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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figure that the FT-DACF IR spectrum is far off from the experimental spectrum. 24 It is<br />
worthwhile to mention that for this open shell system, IR spectra generated applying FT<br />
of velocity autocorrelation function (FT-VACF) has a poorer match than that by FT-<br />
DACF procedure.<br />
Cl 2 .- .H 2<br />
O<br />
Cl 2 .- .2H 2<br />
O (II-B)<br />
IR Intensity<br />
IR Intensity<br />
3000 3200 3400 3600 3800<br />
Frequency (cm -1 )<br />
3000 3200 3400 3600 3800<br />
Frequency (cm -1 )<br />
A<br />
B<br />
Fig. 3.3. Calculated scaled IR spectra at BHHLYP/6-311++G(d,p) level for (A) Cl 2•¯.H 2 O and (B)<br />
Cl 2•¯.2H 2 O. The scaling factor is taken as 0.92 to account for the anharmonic nature of stretching<br />
vibrations. Lorentzian line shape has been applied with peak half-width of 20 cm -1 .<br />
For Cl •− 2 .3H 2 O, Cl •− 2 .4H 2 O and Cl •− 2 .5H 2 O clusters, 10, 15 and 24 minimum<br />
energy structures have been found at BHHLYP/6-311++G(d,p) level, respectively. The<br />
structures which have population of >1% are considered (displayed in Fig. 3.2) and their<br />
population is shown in Table 3. 1. Frequency is also calculated by taking the anharmonic<br />
nature of vibration using vibrational self-consistent field (VSCF) method. As the VSCF<br />
calculation is found to be very costly method for this open shell system, an appropriate<br />
scaling is carried out of the normal mode to include the anharmonic nature of vibrations.<br />
Based on the anhamonic calculation, it is also found that different modes have different<br />
anharmonicity. So different scaling is carried out in the regions having energy range of<br />
64