The mentioned continuous increase in computing power of modern computers
allows for wider and wider applications of theoretical methods supporting experimental research; however, more structurally complex materials such as zeolites still
remain—to large extent—behind theoretical methods, hence the constant need for
simplifications and approximations in theoretical models of real zeolite structures.
The aim of this chapter was to show the applicability of modern theoretical
methods based on the formalism of quantum mechanics for the calculation of
vibrational spectra and structural analysis of aluminosilicate mesoporous materials
from the group of zeolites. The obtained results showed the efficiency of theoretical
methods and their practical usefulness as a tool supporting description and interpretation of vibrational spectra of zeolites and allowed to show that due to the
hierarchical structure of zeolitic materials, it is possible to study their properties
using theoretical models corresponding to structural units from different levels,
which allows obtaining valuable results providing insight into the structure and
properties of such structural units. These results also confirmed the far-reaching
identity of the SBU structural units, manifested by, inter alia, well-defined bands on
vibrational spectra in the mid-infrared range and hence the rationality of the classification of zeolites based on such units.
An important result is also the demonstration that the correct reconstruction of
the spectrum in the far-infrared range, where there are bands associated with lattice
vibrations with positions and intensities strongly dependent on the amount, type,
and nature of the interactions of foreign ions with the aluminosilicate framework, is
possible only using models that take into account translational symmetry of crystal
lattice, which is still a major difficulty due to the enormous structural complexity of
zeolites. Nevertheless, the first results of calculations made for simplified periodic
models corresponding to the structure of zeolite A showed that this approach allows
obtaining vibrational spectra largely consistent with the experiment, creating the
possibility of a more detailed analysis of the impact of extra-framework ions on the
aluminosilicate framework and changes in the structure of zeolite A occurring
during, for example, sorption of heavy metals.
The presented results show the high usability of theoretical methods in the
analysis of properties of zeolites, but at the same time indicate the still large
challenges facing these methods, related to the complexity of real materials.
Looking at the pace at which the computing power of modern computers is
growing, one can hope, however, that in the coming years it will be possible to
conduct in silico experiments on a much wider scale, based on models devoid of the
disadvantages resulting from the necessary far-reaching simplifications mentioned
earlier in this chapter, thanks to which it will be possible to quickly and effectively
study the properties of existing materials and design new ones with required
properties as well as modeling of dynamic processes (such as sorption or catalysis),
and therefore making computational methods an irreplaceable source of information
supplementing the knowledge obtained in experimental research.
Acknowledgements This work was partially supported by the National Science Centre, Poland,
under grant No. 2015/17/B/ST8/01200.
328
M. Król et al.
allows for wider and wider applications of theoretical methods supporting experimental research; however, more structurally complex materials such as zeolites still
remain—to large extent—behind theoretical methods, hence the constant need for
simplifications and approximations in theoretical models of real zeolite structures.
The aim of this chapter was to show the applicability of modern theoretical
methods based on the formalism of quantum mechanics for the calculation of
vibrational spectra and structural analysis of aluminosilicate mesoporous materials
from the group of zeolites. The obtained results showed the efficiency of theoretical
methods and their practical usefulness as a tool supporting description and interpretation of vibrational spectra of zeolites and allowed to show that due to the
hierarchical structure of zeolitic materials, it is possible to study their properties
using theoretical models corresponding to structural units from different levels,
which allows obtaining valuable results providing insight into the structure and
properties of such structural units. These results also confirmed the far-reaching
identity of the SBU structural units, manifested by, inter alia, well-defined bands on
vibrational spectra in the mid-infrared range and hence the rationality of the classification of zeolites based on such units.
An important result is also the demonstration that the correct reconstruction of
the spectrum in the far-infrared range, where there are bands associated with lattice
vibrations with positions and intensities strongly dependent on the amount, type,
and nature of the interactions of foreign ions with the aluminosilicate framework, is
possible only using models that take into account translational symmetry of crystal
lattice, which is still a major difficulty due to the enormous structural complexity of
zeolites. Nevertheless, the first results of calculations made for simplified periodic
models corresponding to the structure of zeolite A showed that this approach allows
obtaining vibrational spectra largely consistent with the experiment, creating the
possibility of a more detailed analysis of the impact of extra-framework ions on the
aluminosilicate framework and changes in the structure of zeolite A occurring
during, for example, sorption of heavy metals.
The presented results show the high usability of theoretical methods in the
analysis of properties of zeolites, but at the same time indicate the still large
challenges facing these methods, related to the complexity of real materials.
Looking at the pace at which the computing power of modern computers is
growing, one can hope, however, that in the coming years it will be possible to
conduct in silico experiments on a much wider scale, based on models devoid of the
disadvantages resulting from the necessary far-reaching simplifications mentioned
earlier in this chapter, thanks to which it will be possible to quickly and effectively
study the properties of existing materials and design new ones with required
properties as well as modeling of dynamic processes (such as sorption or catalysis),
and therefore making computational methods an irreplaceable source of information
supplementing the knowledge obtained in experimental research.
Acknowledgements This work was partially supported by the National Science Centre, Poland,
under grant No. 2015/17/B/ST8/01200.
328
M. Król et al.