Modern Polymer Spect..

132 3 T/ihrtitional Spectra us LL Probe of Structural Order
a
Figure 3-18. Dynaniical data
for the perfect chain of HCl
and DCl based on a valence
force field. (a) Dispersion
curves; (b) k = 0 normal
modes; (c) densities of
vibrational states.
calculated dispersion curves (Figure 3-l8a), density of vibrational states g( 11) (Figure
3-l8b) and vibrational displacements for k = 0 phonons both for pure HCI and
DCI (Figure. 3-18c). Vibrational infrared intensities have also been calculated based
on a simple fixed point-charge model [97].
As a second step, we generated models of chains of HCl containing defects of
DC1. Calculatioiis are made easier because isotopic substitution does not change the
force field. Several mixtures were considered and we will focus here ody on three
cases of mixed chains with 3%, 25% and 45Y” DC1 in HCI. Chains were made up by
600 chemical units.