CHEM01200604005 A. K. Pathak - Homi Bhabha National Institute

3350-3500 cm -1 (scaling factor ~0.93) and 3500-3650 cm -1 (scaling factor ~0.90). The
actual scaling factor is obtained by comparing the harmonic frequency with the
experimentally observed spectrum. As large number of minimum energy structures are
found, weighted average IR spectra are calculated which can be best comparable to the
experimental spectra. The weight factor is calculated based on Boltzmann population at
100K. The weight factor is also calculated at a temperature range from 75K to 200K as
the cluster experiment (NVE ensemble) is carried out in this low temperature range. The
calculated IR spectra ~100K for all this three systems are close to the experimental
spectra. So, based on this scaling factor, weighted average scaled IR spectra are
calculated at 100K for Cl •− 2 .nH 2 O (n=3-5) and are shown in Fig. 3.4(II) along with the
experimental spectrum. An excellent agreement with experimental results is observed.
Table 3.1. Population (P i ) of the conformers of clusters of each size have been calculated based on free
energy change at 100 K (T) following Boltzmann distribution. Structures are shown in Fig. 3.2.
Structure III-A III-B III-C III-D III-E III-F IV-A IV-B IV-C IV-D
Population
0.54 0.04 0.08 0.09 0.22 0.03 0.53 0.17 0.11 0.03
(P i )
Structure IV-E IV-F IV-G IV-H IV-I IV-J IV-K V-A V-B V-C
Population
0.01 0.03 0.05 0.02 0.02 0.02 0.01 0.15 0.11 0.24
(P i )
Structure V-D V-E V-F V-G V-H V-I V-J V-K V-L
Population
0.04 0.05 0.03 0.20 0.04 0.04 0.03 0.02 0.05
(P i )
65