vibrations of the anion sublattice are usually accompanied by Na–O vibrations
bands and the isolation of a band related the vibration associated with the anion
sublattice only seems impossible on the basis of theoretical spectra. This result is
also confirmed by experimental research. Differences in FIR range confirm that the
band associated with vibrations of the anionic sublattice is a part of the complex
band at around 200 cm
−1 ; i.e., it coincides with the band attributed to the Na–O
vibrations. This effect is particularly evident when comparing the spectra of the
chloride and bromide form (Fig. 10.16), where it is possible to observe band
splitting with a maximum at 199 cm
−1 into two component bands at 199 and
162 cm
−1 . Introduction of S
2– ions to the system translates into larger changes also
in the pseudolattice range of vibrational spectrum, suggesting some modification of
this structure, or a change in the oxidation state of sulfur during synthesis.
Summing up, it can be concluded that based on the results of theoretical and
experimental data, it is possible to analyze in detail the structural changes taking
place as a result of the exchange of particular extra-framework ions. It is possible to
assess the deformation of the structure due to ion exchange as well as the unambiguous assignment of bands located both in mid- and in far-infrared region of
vibrational spectrum. The latter can be associated with both vibrations of individual
cationic and anionic sublattices.
10.8 Conclusions
Modern spectroscopic methods, in particular IR spectroscopy, have become an
extremely useful and valuable source of knowledge about the properties and
structure of both amorphous and crystalline materials, especially from the point of
view of their local ordering and chemical bond properties. The direct relations
between the shape of the vibrational spectrum and the structure and chemical
composition, as well as the relative ease of measuring such spectra in different
conditions, allow for not only the analysis of the structure of a given material but
also the observation and analysis of changes occurring in various processes. This is
particularly important in the case of materials used in such processes as sorption or
catalysis, where a key role plays local effects, influencing local structural changes
(creation or breaking of chemical bonds) or more subtle local changes in the
properties of chemical bonds in host framework near guest atoms or molecules
deposited on the surface or located inside channels and structural gaps in mesoporous materials.
On the other hand, the development of both more efficient numerical algorithms
and the dynamic increase in the available computing power of modern computers
allows for the growing number of more and more complex simulations, the
so-called in silico experiments, verified experimentally, providing a lot of useful
information allowing for a better understanding of changes taking place in the
material during various processes and more and more effective design of new
(and modifications to existing) materials with specific functional properties.
10 Vibrational Spectroscopy of Zeolites …
327
bands and the isolation of a band related the vibration associated with the anion
sublattice only seems impossible on the basis of theoretical spectra. This result is
also confirmed by experimental research. Differences in FIR range confirm that the
band associated with vibrations of the anionic sublattice is a part of the complex
band at around 200 cm
−1 ; i.e., it coincides with the band attributed to the Na–O
vibrations. This effect is particularly evident when comparing the spectra of the
chloride and bromide form (Fig. 10.16), where it is possible to observe band
splitting with a maximum at 199 cm
−1 into two component bands at 199 and
162 cm
−1 . Introduction of S
2– ions to the system translates into larger changes also
in the pseudolattice range of vibrational spectrum, suggesting some modification of
this structure, or a change in the oxidation state of sulfur during synthesis.
Summing up, it can be concluded that based on the results of theoretical and
experimental data, it is possible to analyze in detail the structural changes taking
place as a result of the exchange of particular extra-framework ions. It is possible to
assess the deformation of the structure due to ion exchange as well as the unambiguous assignment of bands located both in mid- and in far-infrared region of
vibrational spectrum. The latter can be associated with both vibrations of individual
cationic and anionic sublattices.
10.8 Conclusions
Modern spectroscopic methods, in particular IR spectroscopy, have become an
extremely useful and valuable source of knowledge about the properties and
structure of both amorphous and crystalline materials, especially from the point of
view of their local ordering and chemical bond properties. The direct relations
between the shape of the vibrational spectrum and the structure and chemical
composition, as well as the relative ease of measuring such spectra in different
conditions, allow for not only the analysis of the structure of a given material but
also the observation and analysis of changes occurring in various processes. This is
particularly important in the case of materials used in such processes as sorption or
catalysis, where a key role plays local effects, influencing local structural changes
(creation or breaking of chemical bonds) or more subtle local changes in the
properties of chemical bonds in host framework near guest atoms or molecules
deposited on the surface or located inside channels and structural gaps in mesoporous materials.
On the other hand, the development of both more efficient numerical algorithms
and the dynamic increase in the available computing power of modern computers
allows for the growing number of more and more complex simulations, the
so-called in silico experiments, verified experimentally, providing a lot of useful
information allowing for a better understanding of changes taking place in the
material during various processes and more and more effective design of new
(and modifications to existing) materials with specific functional properties.
10 Vibrational Spectroscopy of Zeolites …
327