An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Crystals of copper-doped barium fluoride borate solid solutions Ba3(BO3)2–xF3x:Cu were grown from... more Crystals of copper-doped barium fluoride borate solid solutions Ba3(BO3)2–xF3x:Cu were grown from high-temperature solution. Using X-ray single-crystal diffraction, the structure was solved and refined in Pbam space group. These crystals are colored in brown, revealing linear dichroism. Optical and electron spin resonance spectroscopic investigations concluded that the light absorption of Ba3(BO3)2–xF3x:Cu crystals is caused by both the exciton and free charge carriers. This phenomenon is similar to those observed in other colored “antizeolites” built with the positively charged framework of porous [Ba12(BO3)6]6+ building blocks (hence named as antizeolites). The coloring of Ba3(BO3)2–xF3x:Cu crystals is associated with the absorption of Cu2+ ions as well. For the first time, constants of the hyperfine interaction of copper ions Cu2+ in octahedral fluorine surroundings [CuF6]4– have been determined.
Crystals of the MnBa(BO)Fphase were grown from a high-temperature solution. This new fluoride bor... more Crystals of the MnBa(BO)Fphase were grown from a high-temperature solution. This new fluoride borate is built of positively charged [Ba(BO)]blocks, the so-called "anti-zeolite" pattern. Using X-ray single-crystal diffraction, the bulk atomic arrangement in the centrosymmetric tetragonal unit cell in I4/mcm could be elucidated. Crystals of the (MnF)group-containing solid solution MnBa(BO)Fare dark brown in color in contrast to the differently colored crystals of (LiF)group-containing "anti-zeolite" LiBa(BO)F(P4bc). According to the electron spin resonance and optical spectroscopic investigation, the absorption spectrum of LiBa(BO)Fcrystals results from the absorption of light by both exciton and free charge carriers and can be tuned by varying the initial composition of the high-temperature solution.
The present study is aimed at unveiling the luminescence potential of Ba4−xSr3+x(BO3)4−yF2+3y (BS... more The present study is aimed at unveiling the luminescence potential of Ba4−xSr3+x(BO3)4−yF2+3y (BSBF) crystals doped with Eu3+, Tb3+, and Ce3+. Owing to the incongruent melting character of the phase, the NaF compound was used as a solvent for BSBF crystal growth. The structure of BSBF: Eu3+ with Eu2O3 concentration of about 0.7(3) wt% was solved in the non-centrosymmetric point group P63mc. The presence of Eu2O3 in BSBF: Eu3+ leads to a shift of the absorption edge from 225 nm to 320 nm. The photoluminescence properties of the BSBF: Ce3+, BSBF: Tb3+, BSBF: Eu3+, and BSBF: Eu3+, Tb3+, Ce3+ crystals have been studied. The unusual feature of europium emission in BSBF is the intensively manifested 5D0→7F0 transition at about 574 nm, which is the strongest for BSBF: Eu3+ at 370 nm excitation and for BSBF: Eu3+, Tb3+, Ce3+ at 300 nm and 370 nm excitations. No evidence of Tb3+→Eu3+ energy transfer was found for BSBF: Eu3+, Tb3+, Ce3+. The PL spectra of BSBF: Eu3+ at 77 and 300 K are simila...
We have studied the polarized optical absorption
and the EPR spectra of Ni-doped beryls grown by
... more We have studied the polarized optical absorption and the EPR spectra of Ni-doped beryls grown by hydrothermal, flux and gas-transport methods, and chrysoberyl grown by the Czochralski and flux methods. In beryls, three groups of bands belonging to three various Ni centres were distinguished by analysis of the absorption band intensities. The first group, bands with maximums at 21740 (E ^ c), 17240 (E || c) and 9260 (E ^ + || c), 7140 (E || + ^ c) cm1, are due to Ni3+ in octahedral Al3+ site. The second group is bands at 25640 (E ^ c), 22220 (E || c) and 13520 (E ||+^ c), 13160 (E ^+|| c) cm1 and 8930 (E ^+|| c), 7460 (E || c) cm1, which are caused by Ni2+ in octahedral Al3+ site. Weak wide bands at 17540 (E ^ c), 15500 (E || c) cm1 and 6580 (E || + ^ c), 5950 (E || c) cm1 are related to Ni2+ in tetrahedral Be2+ site. The occurrence of Ni ions in Be2+ site is proved by the EPR spectra of 1VNi+ in c-irradiated samples. According to the spectra of optical absorption of Ni-doped chrysoberyl, two types of Ni centres have been established: Ni3+ and Ni2+ ions in octahedral Al3+ sites. From the EPR spectra of the X-ray irradiated crystals BeAl2O4: Ni, it follows that 68% of Ni+ ions occupy octahedral Al3+ sites with mirror symmetry and 32% are in Al3+ sites with inversion symmetry. In the approximation of trigonal field with regard to Trees correction, the energy levels of Ni3+ and Ni2+ have been calculated in octahedral and tetrahedral coordination. There is good agreement between the obtained experimental and calculated data. The polarization dependence of the optical absorption bands is well explained in terms of the spin– orbit interaction.
We have studied the polarized optical
absorption and EPR spectra of Co-doped beryls grown
by hydr... more We have studied the polarized optical absorption and EPR spectra of Co-doped beryls grown by hydrothermal, flux, and gas-transport methods, and chrysoberyl grown by the Czochralski method. In beryls three groups of bands, belonging to three various Co centers, were distinguished by analysis of the absorption band intensities. The first group, bands with maxima at 22 220 (E ? c), 17 730 (E k c), and 9090 (E k c), 7520 (E ? c) cm)1 are due to Co2+ in octahedral site of Al3+. The second group is bands at 18 940, 18 250, 17 700 (E ? c), 18 300, 17 700, 17 000 (E k c) and 8830 (E ? c), 7350 (E k c) cm-1 and 5320 (E ? c), 3880 (E k c) cm)1, which are caused by Co2+ in tetrahedral site of Be2+. A weak wide band in flux and gas-transport beryl in the region of 12 500– 8300 cm-1 (E k, ? c) is related to Co3+ in octahedral Al3+ site. In hydrothermal beryl, bands 13 200 (E ? c), 10 900 (E k c), and 8500 (E ? c) cm)1 are caused by an uncontrolled impurity of Cu2+ ions. For Co-doped chrysoberyl one type of center of Co has been established: Co2+ in the octahedral site of Al3+. In the approximation of the trigonal field with regard to Trees’ correction, the energy levels of Co2+ have been calculated in octahedral and tetrahedral coordination. There is good agreement between the obtained experimental and calculated data. The polarization dependence of the optical absorption bands is explained well in terms of the spin-orbit interaction.
It is shown the possibility to determine the coordination of paramagnetic ions in disordered soli... more It is shown the possibility to determine the coordination of paramagnetic ions in disordered solid structures, e.g., in barium borate glasses. For this purpose the electron paramagnetic resonance (EPR) method was used to study a-and b-BaB2O4 crystals and glasses of 45BaO9 55B2O3 and 40BaO9 60B2O3 (mol%) composition activated by Ag+ and Pb2+ ions. After the samples were exposed to X-rays at 77 K, different EPR centers were observed in them. In a-and b-BaB2O4 crystals and glasses the EPR centers Ag2+, Ag0 , Pb+ , Pb3+, and hole centers of O- type were studied. The EPR parameters of these centers and their arrangement in crystal structure were determined. It is shown that Pb3+ ions in b-BaB2O4 crystals occupy Ba2+ position in an irregular polyhedron from the eight oxygen, whereas in a-BaB2O4 crystals they occupy Bf2 position in a sixfold coordination. Pb+ ions in a-BaB2O4 crystals occupy Bf1 position in a ninefold coordination from oxygen. In barium borate glasses, Pb3+ ions were studied in coordination polyhedron from six oxygen atoms and in a polyhedron from nine to ten oxygen atoms. It is assumed that the established difference in the structural position of Pb3+ ions in glasses is due to their previous incorporation in associative cation–anion complexes (AC) and ‘‘free’’ structure-forming cations (FC). Computer simulations have been performed to analyze the stability of specific associative complexes and to compare their bond lengths with experimental data.
Infrared spectra and EPR of channel constituents in beryls synthesized hydrothermally in the pres... more Infrared spectra and EPR of channel constituents in beryls synthesized hydrothermally in the presence of NH4Cl were investigated.
An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Crystals of copper-doped barium fluoride borate solid solutions Ba3(BO3)2–xF3x:Cu were grown from... more Crystals of copper-doped barium fluoride borate solid solutions Ba3(BO3)2–xF3x:Cu were grown from high-temperature solution. Using X-ray single-crystal diffraction, the structure was solved and refined in Pbam space group. These crystals are colored in brown, revealing linear dichroism. Optical and electron spin resonance spectroscopic investigations concluded that the light absorption of Ba3(BO3)2–xF3x:Cu crystals is caused by both the exciton and free charge carriers. This phenomenon is similar to those observed in other colored “antizeolites” built with the positively charged framework of porous [Ba12(BO3)6]6+ building blocks (hence named as antizeolites). The coloring of Ba3(BO3)2–xF3x:Cu crystals is associated with the absorption of Cu2+ ions as well. For the first time, constants of the hyperfine interaction of copper ions Cu2+ in octahedral fluorine surroundings [CuF6]4– have been determined.
Crystals of the MnBa(BO)Fphase were grown from a high-temperature solution. This new fluoride bor... more Crystals of the MnBa(BO)Fphase were grown from a high-temperature solution. This new fluoride borate is built of positively charged [Ba(BO)]blocks, the so-called "anti-zeolite" pattern. Using X-ray single-crystal diffraction, the bulk atomic arrangement in the centrosymmetric tetragonal unit cell in I4/mcm could be elucidated. Crystals of the (MnF)group-containing solid solution MnBa(BO)Fare dark brown in color in contrast to the differently colored crystals of (LiF)group-containing "anti-zeolite" LiBa(BO)F(P4bc). According to the electron spin resonance and optical spectroscopic investigation, the absorption spectrum of LiBa(BO)Fcrystals results from the absorption of light by both exciton and free charge carriers and can be tuned by varying the initial composition of the high-temperature solution.
The present study is aimed at unveiling the luminescence potential of Ba4−xSr3+x(BO3)4−yF2+3y (BS... more The present study is aimed at unveiling the luminescence potential of Ba4−xSr3+x(BO3)4−yF2+3y (BSBF) crystals doped with Eu3+, Tb3+, and Ce3+. Owing to the incongruent melting character of the phase, the NaF compound was used as a solvent for BSBF crystal growth. The structure of BSBF: Eu3+ with Eu2O3 concentration of about 0.7(3) wt% was solved in the non-centrosymmetric point group P63mc. The presence of Eu2O3 in BSBF: Eu3+ leads to a shift of the absorption edge from 225 nm to 320 nm. The photoluminescence properties of the BSBF: Ce3+, BSBF: Tb3+, BSBF: Eu3+, and BSBF: Eu3+, Tb3+, Ce3+ crystals have been studied. The unusual feature of europium emission in BSBF is the intensively manifested 5D0→7F0 transition at about 574 nm, which is the strongest for BSBF: Eu3+ at 370 nm excitation and for BSBF: Eu3+, Tb3+, Ce3+ at 300 nm and 370 nm excitations. No evidence of Tb3+→Eu3+ energy transfer was found for BSBF: Eu3+, Tb3+, Ce3+. The PL spectra of BSBF: Eu3+ at 77 and 300 K are simila...
We have studied the polarized optical absorption
and the EPR spectra of Ni-doped beryls grown by
... more We have studied the polarized optical absorption and the EPR spectra of Ni-doped beryls grown by hydrothermal, flux and gas-transport methods, and chrysoberyl grown by the Czochralski and flux methods. In beryls, three groups of bands belonging to three various Ni centres were distinguished by analysis of the absorption band intensities. The first group, bands with maximums at 21740 (E ^ c), 17240 (E || c) and 9260 (E ^ + || c), 7140 (E || + ^ c) cm1, are due to Ni3+ in octahedral Al3+ site. The second group is bands at 25640 (E ^ c), 22220 (E || c) and 13520 (E ||+^ c), 13160 (E ^+|| c) cm1 and 8930 (E ^+|| c), 7460 (E || c) cm1, which are caused by Ni2+ in octahedral Al3+ site. Weak wide bands at 17540 (E ^ c), 15500 (E || c) cm1 and 6580 (E || + ^ c), 5950 (E || c) cm1 are related to Ni2+ in tetrahedral Be2+ site. The occurrence of Ni ions in Be2+ site is proved by the EPR spectra of 1VNi+ in c-irradiated samples. According to the spectra of optical absorption of Ni-doped chrysoberyl, two types of Ni centres have been established: Ni3+ and Ni2+ ions in octahedral Al3+ sites. From the EPR spectra of the X-ray irradiated crystals BeAl2O4: Ni, it follows that 68% of Ni+ ions occupy octahedral Al3+ sites with mirror symmetry and 32% are in Al3+ sites with inversion symmetry. In the approximation of trigonal field with regard to Trees correction, the energy levels of Ni3+ and Ni2+ have been calculated in octahedral and tetrahedral coordination. There is good agreement between the obtained experimental and calculated data. The polarization dependence of the optical absorption bands is well explained in terms of the spin– orbit interaction.
We have studied the polarized optical
absorption and EPR spectra of Co-doped beryls grown
by hydr... more We have studied the polarized optical absorption and EPR spectra of Co-doped beryls grown by hydrothermal, flux, and gas-transport methods, and chrysoberyl grown by the Czochralski method. In beryls three groups of bands, belonging to three various Co centers, were distinguished by analysis of the absorption band intensities. The first group, bands with maxima at 22 220 (E ? c), 17 730 (E k c), and 9090 (E k c), 7520 (E ? c) cm)1 are due to Co2+ in octahedral site of Al3+. The second group is bands at 18 940, 18 250, 17 700 (E ? c), 18 300, 17 700, 17 000 (E k c) and 8830 (E ? c), 7350 (E k c) cm-1 and 5320 (E ? c), 3880 (E k c) cm)1, which are caused by Co2+ in tetrahedral site of Be2+. A weak wide band in flux and gas-transport beryl in the region of 12 500– 8300 cm-1 (E k, ? c) is related to Co3+ in octahedral Al3+ site. In hydrothermal beryl, bands 13 200 (E ? c), 10 900 (E k c), and 8500 (E ? c) cm)1 are caused by an uncontrolled impurity of Cu2+ ions. For Co-doped chrysoberyl one type of center of Co has been established: Co2+ in the octahedral site of Al3+. In the approximation of the trigonal field with regard to Trees’ correction, the energy levels of Co2+ have been calculated in octahedral and tetrahedral coordination. There is good agreement between the obtained experimental and calculated data. The polarization dependence of the optical absorption bands is explained well in terms of the spin-orbit interaction.
It is shown the possibility to determine the coordination of paramagnetic ions in disordered soli... more It is shown the possibility to determine the coordination of paramagnetic ions in disordered solid structures, e.g., in barium borate glasses. For this purpose the electron paramagnetic resonance (EPR) method was used to study a-and b-BaB2O4 crystals and glasses of 45BaO9 55B2O3 and 40BaO9 60B2O3 (mol%) composition activated by Ag+ and Pb2+ ions. After the samples were exposed to X-rays at 77 K, different EPR centers were observed in them. In a-and b-BaB2O4 crystals and glasses the EPR centers Ag2+, Ag0 , Pb+ , Pb3+, and hole centers of O- type were studied. The EPR parameters of these centers and their arrangement in crystal structure were determined. It is shown that Pb3+ ions in b-BaB2O4 crystals occupy Ba2+ position in an irregular polyhedron from the eight oxygen, whereas in a-BaB2O4 crystals they occupy Bf2 position in a sixfold coordination. Pb+ ions in a-BaB2O4 crystals occupy Bf1 position in a ninefold coordination from oxygen. In barium borate glasses, Pb3+ ions were studied in coordination polyhedron from six oxygen atoms and in a polyhedron from nine to ten oxygen atoms. It is assumed that the established difference in the structural position of Pb3+ ions in glasses is due to their previous incorporation in associative cation–anion complexes (AC) and ‘‘free’’ structure-forming cations (FC). Computer simulations have been performed to analyze the stability of specific associative complexes and to compare their bond lengths with experimental data.
Infrared spectra and EPR of channel constituents in beryls synthesized hydrothermally in the pres... more Infrared spectra and EPR of channel constituents in beryls synthesized hydrothermally in the presence of NH4Cl were investigated.
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and the EPR spectra of Ni-doped beryls grown by
hydrothermal, flux and gas-transport methods, and
chrysoberyl grown by the Czochralski and flux methods.
In beryls, three groups of bands belonging to three various
Ni centres were distinguished by analysis of the
absorption band intensities. The first group, bands
with maximums at 21740 (E ^ c), 17240 (E || c) and 9260
(E ^ + || c), 7140 (E || + ^ c) cm1, are due to Ni3+ in
octahedral Al3+ site. The second group is bands at
25640 (E ^ c), 22220 (E || c) and 13520 (E ||+^ c), 13160
(E ^+|| c) cm1 and 8930 (E ^+|| c), 7460 (E || c) cm1,
which are caused by Ni2+ in octahedral Al3+ site. Weak
wide bands at 17540 (E ^ c), 15500 (E || c) cm1 and 6580
(E || + ^ c), 5950 (E || c) cm1 are related to Ni2+ in
tetrahedral Be2+ site. The occurrence of Ni ions in Be2+
site is proved by the EPR spectra of 1VNi+ in c-irradiated
samples. According to the spectra of optical absorption of
Ni-doped chrysoberyl, two types of Ni centres have been
established: Ni3+ and Ni2+ ions in octahedral Al3+ sites.
From the EPR spectra of the X-ray irradiated crystals
BeAl2O4: Ni, it follows that 68% of Ni+ ions occupy
octahedral Al3+ sites with mirror symmetry and 32% are
in Al3+ sites with inversion symmetry. In the approximation
of trigonal field with regard to Trees correction,
the energy levels of Ni3+ and Ni2+ have been calculated
in octahedral and tetrahedral coordination. There is good
agreement between the obtained experimental and calculated
data. The polarization dependence of the optical
absorption bands is well explained in terms of the spin–
orbit interaction.
absorption and EPR spectra of Co-doped beryls grown
by hydrothermal, flux, and gas-transport methods, and
chrysoberyl grown by the Czochralski method. In
beryls three groups of bands, belonging to three various
Co centers, were distinguished by analysis of the
absorption band intensities. The first group, bands
with maxima at 22 220 (E ? c), 17 730 (E k c), and
9090 (E k c), 7520 (E ? c) cm)1 are due to Co2+ in
octahedral site of Al3+. The second group is bands at
18 940, 18 250, 17 700 (E ? c), 18 300, 17 700, 17 000
(E k c) and 8830 (E ? c), 7350 (E k c) cm-1 and 5320
(E ? c), 3880 (E k c) cm)1, which are caused by Co2+
in tetrahedral site of Be2+. A weak wide band in flux
and gas-transport beryl in the region of 12 500–
8300 cm-1 (E k, ? c) is related to Co3+ in octahedral
Al3+ site. In hydrothermal beryl, bands 13 200
(E ? c), 10 900 (E k c), and 8500 (E ? c) cm)1 are
caused by an uncontrolled impurity of Cu2+ ions. For
Co-doped chrysoberyl one type of center of Co has
been established: Co2+ in the octahedral site of Al3+.
In the approximation of the trigonal field with regard
to Trees’ correction, the energy levels of Co2+ have
been calculated in octahedral and tetrahedral coordination.
There is good agreement between the obtained
experimental and calculated data. The polarization
dependence of the optical absorption bands is
explained well in terms of the spin-orbit interaction.
were observed in them. In a-and b-BaB2O4 crystals and
glasses the EPR centers Ag2+, Ag0 , Pb+ , Pb3+, and hole
centers of O- type were studied. The EPR parameters of
these centers and their arrangement in crystal structure
were determined. It is shown that Pb3+ ions in b-BaB2O4
crystals occupy Ba2+ position in an irregular polyhedron
from the eight oxygen, whereas in a-BaB2O4 crystals they
occupy Bf2 position in a sixfold coordination. Pb+ ions in
a-BaB2O4 crystals occupy Bf1 position in a ninefold
coordination from oxygen. In barium borate glasses, Pb3+
ions were studied in coordination polyhedron from six
oxygen atoms and in a polyhedron from nine to ten oxygen
atoms. It is assumed that the established difference in the
structural position of Pb3+ ions in glasses is due to their
previous incorporation in associative cation–anion complexes
(AC) and ‘‘free’’ structure-forming cations (FC).
Computer simulations have been performed to analyze the
stability of specific associative complexes and to compare
their bond lengths with experimental data.
and the EPR spectra of Ni-doped beryls grown by
hydrothermal, flux and gas-transport methods, and
chrysoberyl grown by the Czochralski and flux methods.
In beryls, three groups of bands belonging to three various
Ni centres were distinguished by analysis of the
absorption band intensities. The first group, bands
with maximums at 21740 (E ^ c), 17240 (E || c) and 9260
(E ^ + || c), 7140 (E || + ^ c) cm1, are due to Ni3+ in
octahedral Al3+ site. The second group is bands at
25640 (E ^ c), 22220 (E || c) and 13520 (E ||+^ c), 13160
(E ^+|| c) cm1 and 8930 (E ^+|| c), 7460 (E || c) cm1,
which are caused by Ni2+ in octahedral Al3+ site. Weak
wide bands at 17540 (E ^ c), 15500 (E || c) cm1 and 6580
(E || + ^ c), 5950 (E || c) cm1 are related to Ni2+ in
tetrahedral Be2+ site. The occurrence of Ni ions in Be2+
site is proved by the EPR spectra of 1VNi+ in c-irradiated
samples. According to the spectra of optical absorption of
Ni-doped chrysoberyl, two types of Ni centres have been
established: Ni3+ and Ni2+ ions in octahedral Al3+ sites.
From the EPR spectra of the X-ray irradiated crystals
BeAl2O4: Ni, it follows that 68% of Ni+ ions occupy
octahedral Al3+ sites with mirror symmetry and 32% are
in Al3+ sites with inversion symmetry. In the approximation
of trigonal field with regard to Trees correction,
the energy levels of Ni3+ and Ni2+ have been calculated
in octahedral and tetrahedral coordination. There is good
agreement between the obtained experimental and calculated
data. The polarization dependence of the optical
absorption bands is well explained in terms of the spin–
orbit interaction.
absorption and EPR spectra of Co-doped beryls grown
by hydrothermal, flux, and gas-transport methods, and
chrysoberyl grown by the Czochralski method. In
beryls three groups of bands, belonging to three various
Co centers, were distinguished by analysis of the
absorption band intensities. The first group, bands
with maxima at 22 220 (E ? c), 17 730 (E k c), and
9090 (E k c), 7520 (E ? c) cm)1 are due to Co2+ in
octahedral site of Al3+. The second group is bands at
18 940, 18 250, 17 700 (E ? c), 18 300, 17 700, 17 000
(E k c) and 8830 (E ? c), 7350 (E k c) cm-1 and 5320
(E ? c), 3880 (E k c) cm)1, which are caused by Co2+
in tetrahedral site of Be2+. A weak wide band in flux
and gas-transport beryl in the region of 12 500–
8300 cm-1 (E k, ? c) is related to Co3+ in octahedral
Al3+ site. In hydrothermal beryl, bands 13 200
(E ? c), 10 900 (E k c), and 8500 (E ? c) cm)1 are
caused by an uncontrolled impurity of Cu2+ ions. For
Co-doped chrysoberyl one type of center of Co has
been established: Co2+ in the octahedral site of Al3+.
In the approximation of the trigonal field with regard
to Trees’ correction, the energy levels of Co2+ have
been calculated in octahedral and tetrahedral coordination.
There is good agreement between the obtained
experimental and calculated data. The polarization
dependence of the optical absorption bands is
explained well in terms of the spin-orbit interaction.
were observed in them. In a-and b-BaB2O4 crystals and
glasses the EPR centers Ag2+, Ag0 , Pb+ , Pb3+, and hole
centers of O- type were studied. The EPR parameters of
these centers and their arrangement in crystal structure
were determined. It is shown that Pb3+ ions in b-BaB2O4
crystals occupy Ba2+ position in an irregular polyhedron
from the eight oxygen, whereas in a-BaB2O4 crystals they
occupy Bf2 position in a sixfold coordination. Pb+ ions in
a-BaB2O4 crystals occupy Bf1 position in a ninefold
coordination from oxygen. In barium borate glasses, Pb3+
ions were studied in coordination polyhedron from six
oxygen atoms and in a polyhedron from nine to ten oxygen
atoms. It is assumed that the established difference in the
structural position of Pb3+ ions in glasses is due to their
previous incorporation in associative cation–anion complexes
(AC) and ‘‘free’’ structure-forming cations (FC).
Computer simulations have been performed to analyze the
stability of specific associative complexes and to compare
their bond lengths with experimental data.