diverse physicochemical properties shows versatile possibilities of using these
minerals [4].
Among many experimental methods used to characterize the structure of zeolites, spectroscopic methods such as vibrational spectroscopy (IR and Raman) and
nuclear magnetic resonance (NMR) spectroscopy (providing primary information
about the near and middle range ordering) occupy a special place [6, 7]. Presented
work is mainly devoted to the analysis of experimental vibrational spectra of
zeolites based on the results of quantum mechanical calculations. The detailed
interpretation of experimental spectra was based on the identification of bands
related to vibrations of characteristic structural elements of zeolites. The identification of these bands provides information related to both, the framework structure
itself and the influence of the above-mentioned extra-framework cations introduced
into the structure on spectra envelope.
10.2 Systematics of Zeolite-Type Crystals
The tetrahedral structure of zeolites can be considered as a set of spatially connected
structural units—the so-called SBU (secondary building unit)—built of silicon and
aluminum tetrahedral ([SiO 4 ] and [AlO 4 ], respectively), i.e., PBU (primary building
units) [8]. SBUs can be a single or double rings of different sizes (e.g., S4R—single
4-ring, D6R—double 6-ring) or more complex tetrahedral units (e.g., 4=1 or 5–1
units). Figure 10.1 shows schematically several selected SBUs observed in zeolite
structures [9]. By linking together, these units form distinctive types of chambers
and channels, e.g., periodically reproducible CBUs (composite building units), such
as a-cage, b-cage (sodalite cage), or e-cage (cancrinite cage) [9]. Only taking into
account all three mentioned levels of hierarchy of construction of zeolite structure
gives a spatial framework that determines the properties of these materials [10].
Fig. 10.1 Examples of secondary building units (SBUs) occurring in zeolite structures: S4R (a),
S6R (b), S8R (c), D4R (d); and more complex fragment of LTA-type structure (e)
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minerals [4].
Among many experimental methods used to characterize the structure of zeolites, spectroscopic methods such as vibrational spectroscopy (IR and Raman) and
nuclear magnetic resonance (NMR) spectroscopy (providing primary information
about the near and middle range ordering) occupy a special place [6, 7]. Presented
work is mainly devoted to the analysis of experimental vibrational spectra of
zeolites based on the results of quantum mechanical calculations. The detailed
interpretation of experimental spectra was based on the identification of bands
related to vibrations of characteristic structural elements of zeolites. The identification of these bands provides information related to both, the framework structure
itself and the influence of the above-mentioned extra-framework cations introduced
into the structure on spectra envelope.
10.2 Systematics of Zeolite-Type Crystals
The tetrahedral structure of zeolites can be considered as a set of spatially connected
structural units—the so-called SBU (secondary building unit)—built of silicon and
aluminum tetrahedral ([SiO 4 ] and [AlO 4 ], respectively), i.e., PBU (primary building
units) [8]. SBUs can be a single or double rings of different sizes (e.g., S4R—single
4-ring, D6R—double 6-ring) or more complex tetrahedral units (e.g., 4=1 or 5–1
units). Figure 10.1 shows schematically several selected SBUs observed in zeolite
structures [9]. By linking together, these units form distinctive types of chambers
and channels, e.g., periodically reproducible CBUs (composite building units), such
as a-cage, b-cage (sodalite cage), or e-cage (cancrinite cage) [9]. Only taking into
account all three mentioned levels of hierarchy of construction of zeolite structure
gives a spatial framework that determines the properties of these materials [10].
Fig. 10.1 Examples of secondary building units (SBUs) occurring in zeolite structures: S4R (a),
S6R (b), S8R (c), D4R (d); and more complex fragment of LTA-type structure (e)
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M. Król et al.