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Luca Bindi - One of the best experts on this subject based on the ideXlab platform.

  • from ancient pigments to modern optoelectronic applications of Arsenic Sulfides bonazziite the natural analogue of β as4s4 from khaidarkan deposit kyrgyzstan
    Mineralogical Magazine, 2015
    Co-Authors: Luca Bindi, G Pratesi, Maurizio Munizmiranda, Matteo Zoppi, Laura Chelazzi, Giovanni Orazio Lepore, Silvio Menchetti
    Abstract:

    Bonazziite is a new mineral from Khaidarkan deposit, Kyrgyzstan and represents the natural analogue of the β-form of the well known As4S4 compound. It occurs as rare crystals up to 100 μm across associated with realgar, sulfur, wakabayashilite, alacranite, non-stoichiometric As4S4+ x Sulfides and stibnite in a calcite matrix. In thick section, bonazziite is opaque with a resinous lustre and a dark-orange streak. It is brittle; the Vickers hardness (VHN15) is 70 kg/mm2 (range: 60–76) (Mohs hardness of ~2½). In plane-polarized incident light, bonazziite is strongly bireflectant and pleochroic from orange to light red. The mineral shows orange to red internal reflections. Between crossed polars, the mineral is strongly anisotropic with greyish to light-blue rotation tints. Reflectance percentages in air for R min and R max are 19.9, 22.2 (471.1 nm), 19.1, 21.3 (548.3 nm), 18.8, 19.7 (586.6 nm) and 17.8, 18.9 (652.3 nm), respectively. Bonazziite is monoclinic, space group C 2/ c , with a = 9.956(1), b = 9.308(1), c = 8.869(1) A, β = 102.55(2)° and V = 802.3(2) A3, Z = 4. The crystal structure [ R 1 = 0.0263 for 735 reflections with F o > 4σ( F o)] is based on the As4S4 cage-like molecule, in which each As atom links one As and two S atoms. The As4S4 molecule is identical to that found in the structure of realgar. The six strongest powder diffraction lines [ d in A ( I/I ) ( hkl )] are: 5.74 (100) (1I11); 4.10 (60) (021); 3.92 (50) (1I12); 3.12 (60) (022, 310); 2.95 (50) (221, 202); 2.86 (80) (2I22, 1I31). A mean of six electron microprobe analyses gave the formula As3.95S4.05, on the basis of eight atoms. The new mineral has been approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (IMA No. 2013-141) and named for Paola Bonazzi, in recognition of her seminal contributions to the study of Arsenic Sulfides and their alteration induced by exposure to light.

  • structural and vibrational properties of Arsenic Sulfides alacranite as8s9
    Journal of Physical Chemistry A, 2011
    Co-Authors: Marco Pagliai, Luca Bindi, Maurizio Munizmiranda, Paola Bonazzi, Gianni Cardini
    Abstract:

    Alacranite, As8S9, has been studied by a combined approach based on micro-Raman measurements and ab initio molecular dynamics simulations, with the Car−Parrinello method. The structure of this arse...

  • A crystallographic review of Arsenic Sulfides : effects of chemical variations and changes induced by exposure to light
    Zeitschrift für Kristallographie - Crystalline Materials, 2008
    Co-Authors: Paola Bonazzi, Luca Bindi
    Abstract:

    Crystal data for natural and synthetic Arsenic Sulfides are reported and discussed. Most of them [a- and β-dimorphite, realgar, β-As 4 S 4 phase, pararealgar, Kutoglu's As 4 S 4 (II) phase, alacranite, uzonite, orthorhombic As 4 S 5 phase] have a crystal structure consisting of a packing of cage-like, covalently bonded As 4 S n (n = 3, 4 and 5) molecules held together by weak interactions of van der Waals character. Their structures are compared in terms of molecular packing and molecular parameters. The layered structural arrangement of orpiment, As 2 S 3 , is described and the effects of the incorporation of Se replacing for S is discussed. The structures of wakabayashilite and getchellite, which contain mixed (As, Sb) coordination polyhedra, are also described to outline the geometric effects of the Sb → As substitution. The results of recent studies dealing with the effects of the exposure of realgar or other Arsenic Sulfides to visible light are reported and discussed. Their interest in the study of Arsenical pigments and their preservation in artwork is outlined with some examples of application.

  • light induced alteration of Arsenic Sulfides a new product with an orthorhombic crystal structure
    American Mineralogist, 2007
    Co-Authors: Luca Bindi, Paola Bonazzi
    Abstract:

    The crystal structure of a new light-induced alteration product obtained from a natural non-stoichiometric Arsenic sulÞ de (original chemical formula As4S4.35) was solved in the space group Pccn, and reÞ ned to a Þ nal R index of 9.89%. Unit-cell parameters are: a = 19.352(7), b = 10.166(3), c = 8.697(4) A, V = 1711(1) A 3 ; Z = 8. The structural reÞ nement results yielded a chemical formula close to As4S5. The structure consists of discrete, covalently bonded As4S5 molecules, which are held together by van der Waals forces. The molecular packing is similar to that of the original crystal, which, in turn, is the same as to that of β-As4S4. The phase originated from a continuous, room-temperature, lightinduced alteration process that does not require a complete rearrangement of the molecular packing and therefore does not imply the loss of coherency between crystalline domains.

  • light induced changes in molecular Arsenic Sulfides state of the art and new evidence by single crystal x ray diffraction
    American Mineralogist, 2006
    Co-Authors: Paola Bonazzi, Luca Bindi, G Pratesi, Silvio Menchetti
    Abstract:

    Light-induced structural changes in single crystals belonging to the β-As 4 S 4 -As 8 S 9 series and in a crystal of synthetic β-As 4 S 3 were monitored step by step by determining the unit-cell dimensions. A marked increase of unit-cell volume as a function of exposure time was observed for all the crystals belonging to the β-As 4 S 4 -As 8 S 9 series except for stoichiometric alacranite (As 8 S 9 ). No significant change upon long exposures to light was observed for the synthetic β-As 4 S 3 crystal. Crystal structure refinements were carried out for crystals with different composition at selected steps of the light-induced process. The structural results clearly showed that the percentage of the As 4 S 5 molecule in the structure increases when a crystal is exposed to light. Therefore, the increment of the unit-cell volume induced by light exposure appears to be related to a random replacement of As 4 S 5 for As 4 S 4 in the structure according to the reaction 5As 4 S 4 + 3O 2 → 4As 4 S 5 + 2As 2 O 3 . The results obtained in the present study combined with a critical review of data previously published indicate that the As 4 S 4 molecule is able to incorporate sulfur to convert to As 4 S 5 upon exposure to light, whereas either As 4 S 3 or As 4 S 5 molecules do not go undergo any modification. It appears that the extent of sulfur incorporation is strictly controlled by the type of molecular packing as well as by the kind of molecule. A final, complete conversion to pararealgar was observed only for pure β-As 4 S 4 , whereas non-stoichiometric As 8 S 9−x crystals initially containing variable amounts of β-As 4 S 4 microdomains convert only partially to pararealgar upon light exposure.

Jucai Yang - One of the best experts on this subject based on the ideXlab platform.

  • Study on electronic structures and properties of neutral and charged Arsenic Sulfides [As n S3 ((-1,0,+1)), n =1-6] with the Gaussian-3 scheme.
    Journal of molecular modeling, 2015
    Co-Authors: Bin Liu, Jucai Yang
    Abstract:

    The structures and energies of neutral and charged Arsenic Sulfides As n S3 ((-1,0,+1)) (n = 1-6) were studied systematically with the G3 method. The ground-state structures of these species are reported. The ground-state structures of As n S3 with n ≥ 4 can be considered as resulting from the replacement of an As atom of the ground-state structure of neutral As n+1S2 by an S atom. In neutral As n S3, the character of sulfur bonding is edge-bridging. The ground-state structures of anion As n S3 (-) sometimes differ from their corresponding neutral structures. In such case, they exhibit a terminal sulfur atom. The ground-state structures of cationic As n S3 (+) are also sometimes different from the corresponding neutral ones. There, sulfur bonding can exhibit face-capping and Arsenic can be four-fold coordinated. The potential energy surfaces of As4S3 (+) and As5S3 (+) are very flat and co-existence of various isomers of As4S3 (+) and As5S3 (+) is possible. Reliable adiabatic electron affinities (AEAs) and adiabatic ionization potentials (AIPs) of As n S3 are predicted. There are odd-even alternations in both AEAs and AIPs as a function of size. In addition, the reliable vertical detachment energies (VDEs) and vertical ionization potentials (VIPs) are presented. The dissociation energies (DEs) of S (and/or its ion S((-/+))) from As n S3 species and their ions were calculated to examine relative stabilities. The hardnesses and HOMO-LUMO gaps of As n S3 (n = 1-6) were evaluated and used to discuss relative chemical reactivity.

  • study on electronic structures and properties of neutral and charged Arsenic Sulfides as n s3 1 0 1 n 1 6 with the gaussian 3 scheme
    Journal of Molecular Modeling, 2015
    Co-Authors: Bin Liu, Jucai Yang
    Abstract:

    The structures and energies of neutral and charged Arsenic Sulfides As n S3 ((-1,0,+1)) (n = 1-6) were studied systematically with the G3 method. The ground-state structures of these species are reported. The ground-state structures of As n S3 with n ≥ 4 can be considered as resulting from the replacement of an As atom of the ground-state structure of neutral As n+1S2 by an S atom. In neutral As n S3, the character of sulfur bonding is edge-bridging. The ground-state structures of anion As n S3 (-) sometimes differ from their corresponding neutral structures. In such case, they exhibit a terminal sulfur atom. The ground-state structures of cationic As n S3 (+) are also sometimes different from the corresponding neutral ones. There, sulfur bonding can exhibit face-capping and Arsenic can be four-fold coordinated. The potential energy surfaces of As4S3 (+) and As5S3 (+) are very flat and co-existence of various isomers of As4S3 (+) and As5S3 (+) is possible. Reliable adiabatic electron affinities (AEAs) and adiabatic ionization potentials (AIPs) of As n S3 are predicted. There are odd-even alternations in both AEAs and AIPs as a function of size. In addition, the reliable vertical detachment energies (VDEs) and vertical ionization potentials (VIPs) are presented. The dissociation energies (DEs) of S (and/or its ion S((-/+))) from As n S3 species and their ions were calculated to examine relative stabilities. The hardnesses and HOMO-LUMO gaps of As n S3 (n = 1-6) were evaluated and used to discuss relative chemical reactivity.

  • Probing the electronic structures and properties of neutral and charged Arsenic Sulfides [As n S 2 (−1,0,+1) , n = 1–6] with Gaussian-3 theory
    Journal of molecular modeling, 2014
    Co-Authors: Liyuan Hou, Jucai Yang, Hongmei Ning
    Abstract:

    The structures and energies of neutral and charged Arsenic Sulfides As n S2 (−1,0,+1) (n = 1–6) were investigated systematically by means of the Gaussian-3 (G3) scheme. The ground-state structures of these species are presented. The ground-state structures of As n S2 can be viewed as the lowest-energy structure of neutral As n+1S by replacing an As atom with a S atom. To be more precise, the ground-state structures of As n S2 can be viewed as the lowest-energy structure of neutral As n+2 by replacing two As atoms with two S atoms, in which the feature of sulfur bonding is edge-bridging. No rule could be found for the ground state structure of As n S2 − and As n S2 +. In As n S2 −, the feature of sulfur bonding is either edge-bridging or a terminal atom, and in AsnS2 + the feature of sulfur bonding is edge-bridging analogous to As n S2. The potential energy surfaces of As4S2 and its charged species are very flat. So co-existence for many isomers of As4S2 and its charged species are possible. The reliable adiabatic electron affinities (AEAs) and adiabatic ionization potentials (AIPs) of As n S2 were estimated. There are odd-even alternations in both AEAs and AIPs as a function of size of As n S2. The dissociation energies (DEs) of S [and/or its ion S(−/+)] from As n S2 clusters and their ions were calculated and used to reveal relative stability.

  • probing the electronic structures and properties of neutral and charged Arsenic Sulfides as n s 2 1 0 1 n 1 6 with gaussian 3 theory
    Journal of Molecular Modeling, 2014
    Co-Authors: Liyuan Hou, Jucai Yang, Hongmei Ning
    Abstract:

    The structures and energies of neutral and charged Arsenic Sulfides As n S2 (−1,0,+1) (n = 1–6) were investigated systematically by means of the Gaussian-3 (G3) scheme. The ground-state structures of these species are presented. The ground-state structures of As n S2 can be viewed as the lowest-energy structure of neutral As n+1S by replacing an As atom with a S atom. To be more precise, the ground-state structures of As n S2 can be viewed as the lowest-energy structure of neutral As n+2 by replacing two As atoms with two S atoms, in which the feature of sulfur bonding is edge-bridging. No rule could be found for the ground state structure of As n S2 − and As n S2 +. In As n S2 −, the feature of sulfur bonding is either edge-bridging or a terminal atom, and in AsnS2 + the feature of sulfur bonding is edge-bridging analogous to As n S2. The potential energy surfaces of As4S2 and its charged species are very flat. So co-existence for many isomers of As4S2 and its charged species are possible. The reliable adiabatic electron affinities (AEAs) and adiabatic ionization potentials (AIPs) of As n S2 were estimated. There are odd-even alternations in both AEAs and AIPs as a function of size of As n S2. The dissociation energies (DEs) of S [and/or its ion S(−/+)] from As n S2 clusters and their ions were calculated and used to reveal relative stability.

  • Probing the electronic structures and properties of neutral and charged Arsenic Sulfides [AsnS2(−1,0,+1), n = 1–6] with Gaussian-3 theory
    Journal of molecular modeling, 2013
    Co-Authors: Jucai Yang, Yali Kang, Xi Wang, Xue Bai
    Abstract:

    The structures and energies of neutral and charged Arsenic Sulfides As(n)S(⁻¹,⁰,⁺¹) (n =1-7) were systematically investigated using the G3 method. The bonding properties and the stabilities of As(n)S and their ions were discussed. The adiabatic electron affinities (AEAs) and adiabatic ionization potentials (AIPs) were presented. The ground-state structures of As(n)S can be considered as the lowest-energy structure of neutral As(n+1) by replacing an As atom with a S atom, that is, "substitutional structure", in which the feature of sulfur bonding is edge-bridging. The ground-state structures of As(n)S⁺ tend to be derived from the lowest-energy structure of cation As(n)⁺ by attaching to a S atom, that is, "attaching structure", in which the sulfur can be three-fold coordinated. There is no rule to be found for the ground-state structure of anion As(n)S⁻, in which the sulfur can be a terminal atom. There are odd-even alternations in both AEAs and AIPs as a function of size of As(n)S. The dissociation energies of S, S⁻, and/or S⁺ from neutral As(n)S and their ions were calculated to examine their stabilities.

Paola Bonazzi - One of the best experts on this subject based on the ideXlab platform.

  • structural and vibrational properties of Arsenic Sulfides alacranite as8s9
    Journal of Physical Chemistry A, 2011
    Co-Authors: Marco Pagliai, Luca Bindi, Maurizio Munizmiranda, Paola Bonazzi, Gianni Cardini
    Abstract:

    Alacranite, As8S9, has been studied by a combined approach based on micro-Raman measurements and ab initio molecular dynamics simulations, with the Car−Parrinello method. The structure of this arse...

  • A crystallographic review of Arsenic Sulfides : effects of chemical variations and changes induced by exposure to light
    Zeitschrift für Kristallographie - Crystalline Materials, 2008
    Co-Authors: Paola Bonazzi, Luca Bindi
    Abstract:

    Crystal data for natural and synthetic Arsenic Sulfides are reported and discussed. Most of them [a- and β-dimorphite, realgar, β-As 4 S 4 phase, pararealgar, Kutoglu's As 4 S 4 (II) phase, alacranite, uzonite, orthorhombic As 4 S 5 phase] have a crystal structure consisting of a packing of cage-like, covalently bonded As 4 S n (n = 3, 4 and 5) molecules held together by weak interactions of van der Waals character. Their structures are compared in terms of molecular packing and molecular parameters. The layered structural arrangement of orpiment, As 2 S 3 , is described and the effects of the incorporation of Se replacing for S is discussed. The structures of wakabayashilite and getchellite, which contain mixed (As, Sb) coordination polyhedra, are also described to outline the geometric effects of the Sb → As substitution. The results of recent studies dealing with the effects of the exposure of realgar or other Arsenic Sulfides to visible light are reported and discussed. Their interest in the study of Arsenical pigments and their preservation in artwork is outlined with some examples of application.

  • light induced alteration of Arsenic Sulfides a new product with an orthorhombic crystal structure
    American Mineralogist, 2007
    Co-Authors: Luca Bindi, Paola Bonazzi
    Abstract:

    The crystal structure of a new light-induced alteration product obtained from a natural non-stoichiometric Arsenic sulÞ de (original chemical formula As4S4.35) was solved in the space group Pccn, and reÞ ned to a Þ nal R index of 9.89%. Unit-cell parameters are: a = 19.352(7), b = 10.166(3), c = 8.697(4) A, V = 1711(1) A 3 ; Z = 8. The structural reÞ nement results yielded a chemical formula close to As4S5. The structure consists of discrete, covalently bonded As4S5 molecules, which are held together by van der Waals forces. The molecular packing is similar to that of the original crystal, which, in turn, is the same as to that of β-As4S4. The phase originated from a continuous, room-temperature, lightinduced alteration process that does not require a complete rearrangement of the molecular packing and therefore does not imply the loss of coherency between crystalline domains.

  • light induced changes in molecular Arsenic Sulfides state of the art and new evidence by single crystal x ray diffraction
    American Mineralogist, 2006
    Co-Authors: Paola Bonazzi, Luca Bindi, G Pratesi, Silvio Menchetti
    Abstract:

    Light-induced structural changes in single crystals belonging to the β-As 4 S 4 -As 8 S 9 series and in a crystal of synthetic β-As 4 S 3 were monitored step by step by determining the unit-cell dimensions. A marked increase of unit-cell volume as a function of exposure time was observed for all the crystals belonging to the β-As 4 S 4 -As 8 S 9 series except for stoichiometric alacranite (As 8 S 9 ). No significant change upon long exposures to light was observed for the synthetic β-As 4 S 3 crystal. Crystal structure refinements were carried out for crystals with different composition at selected steps of the light-induced process. The structural results clearly showed that the percentage of the As 4 S 5 molecule in the structure increases when a crystal is exposed to light. Therefore, the increment of the unit-cell volume induced by light exposure appears to be related to a random replacement of As 4 S 5 for As 4 S 4 in the structure according to the reaction 5As 4 S 4 + 3O 2 → 4As 4 S 5 + 2As 2 O 3 . The results obtained in the present study combined with a critical review of data previously published indicate that the As 4 S 4 molecule is able to incorporate sulfur to convert to As 4 S 5 upon exposure to light, whereas either As 4 S 3 or As 4 S 5 molecules do not go undergo any modification. It appears that the extent of sulfur incorporation is strictly controlled by the type of molecular packing as well as by the kind of molecule. A final, complete conversion to pararealgar was observed only for pure β-As 4 S 4 , whereas non-stoichiometric As 8 S 9−x crystals initially containing variable amounts of β-As 4 S 4 microdomains convert only partially to pararealgar upon light exposure.

Silvio Menchetti - One of the best experts on this subject based on the ideXlab platform.

  • from ancient pigments to modern optoelectronic applications of Arsenic Sulfides bonazziite the natural analogue of β as4s4 from khaidarkan deposit kyrgyzstan
    Mineralogical Magazine, 2015
    Co-Authors: Luca Bindi, G Pratesi, Maurizio Munizmiranda, Matteo Zoppi, Laura Chelazzi, Giovanni Orazio Lepore, Silvio Menchetti
    Abstract:

    Bonazziite is a new mineral from Khaidarkan deposit, Kyrgyzstan and represents the natural analogue of the β-form of the well known As4S4 compound. It occurs as rare crystals up to 100 μm across associated with realgar, sulfur, wakabayashilite, alacranite, non-stoichiometric As4S4+ x Sulfides and stibnite in a calcite matrix. In thick section, bonazziite is opaque with a resinous lustre and a dark-orange streak. It is brittle; the Vickers hardness (VHN15) is 70 kg/mm2 (range: 60–76) (Mohs hardness of ~2½). In plane-polarized incident light, bonazziite is strongly bireflectant and pleochroic from orange to light red. The mineral shows orange to red internal reflections. Between crossed polars, the mineral is strongly anisotropic with greyish to light-blue rotation tints. Reflectance percentages in air for R min and R max are 19.9, 22.2 (471.1 nm), 19.1, 21.3 (548.3 nm), 18.8, 19.7 (586.6 nm) and 17.8, 18.9 (652.3 nm), respectively. Bonazziite is monoclinic, space group C 2/ c , with a = 9.956(1), b = 9.308(1), c = 8.869(1) A, β = 102.55(2)° and V = 802.3(2) A3, Z = 4. The crystal structure [ R 1 = 0.0263 for 735 reflections with F o > 4σ( F o)] is based on the As4S4 cage-like molecule, in which each As atom links one As and two S atoms. The As4S4 molecule is identical to that found in the structure of realgar. The six strongest powder diffraction lines [ d in A ( I/I ) ( hkl )] are: 5.74 (100) (1I11); 4.10 (60) (021); 3.92 (50) (1I12); 3.12 (60) (022, 310); 2.95 (50) (221, 202); 2.86 (80) (2I22, 1I31). A mean of six electron microprobe analyses gave the formula As3.95S4.05, on the basis of eight atoms. The new mineral has been approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (IMA No. 2013-141) and named for Paola Bonazzi, in recognition of her seminal contributions to the study of Arsenic Sulfides and their alteration induced by exposure to light.

  • light induced changes in molecular Arsenic Sulfides state of the art and new evidence by single crystal x ray diffraction
    American Mineralogist, 2006
    Co-Authors: Paola Bonazzi, Luca Bindi, G Pratesi, Silvio Menchetti
    Abstract:

    Light-induced structural changes in single crystals belonging to the β-As 4 S 4 -As 8 S 9 series and in a crystal of synthetic β-As 4 S 3 were monitored step by step by determining the unit-cell dimensions. A marked increase of unit-cell volume as a function of exposure time was observed for all the crystals belonging to the β-As 4 S 4 -As 8 S 9 series except for stoichiometric alacranite (As 8 S 9 ). No significant change upon long exposures to light was observed for the synthetic β-As 4 S 3 crystal. Crystal structure refinements were carried out for crystals with different composition at selected steps of the light-induced process. The structural results clearly showed that the percentage of the As 4 S 5 molecule in the structure increases when a crystal is exposed to light. Therefore, the increment of the unit-cell volume induced by light exposure appears to be related to a random replacement of As 4 S 5 for As 4 S 4 in the structure according to the reaction 5As 4 S 4 + 3O 2 → 4As 4 S 5 + 2As 2 O 3 . The results obtained in the present study combined with a critical review of data previously published indicate that the As 4 S 4 molecule is able to incorporate sulfur to convert to As 4 S 5 upon exposure to light, whereas either As 4 S 3 or As 4 S 5 molecules do not go undergo any modification. It appears that the extent of sulfur incorporation is strictly controlled by the type of molecular packing as well as by the kind of molecule. A final, complete conversion to pararealgar was observed only for pure β-As 4 S 4 , whereas non-stoichiometric As 8 S 9−x crystals initially containing variable amounts of β-As 4 S 4 microdomains convert only partially to pararealgar upon light exposure.

O Shpotyuk - One of the best experts on this subject based on the ideXlab platform.

  • positron annihilation lifetime study of atomic imperfections in nanostructurized solids on the parameterized trapping in wet milled Arsenic Sulfides as4s4
    Physica Status Solidi B-basic Solid State Physics, 2016
    Co-Authors: O Shpotyuk, Zdenka Bujňáková, A Ingram, Jacek Filipecki, Peter Baláž
    Abstract:

    The phenomenon of positron–electron annihilation in lifetime measuring mode is considered as a tool to study nanostructurization in solids possessing mixed positron and positronium (Ps) trapping. Structural inhomogeneities due to guest nanoparticles in such solids are described in terms of substitution trapping in positron- and Ps-related sites within the same host matrix. The developed approach allows estimation of interfacial free-volume voids as being responsible for positron trapping and defect-free bulk positron lifetimes of nanoparticle-modified solids. For the example of Arsenic sulfide, As4S4 nanoparticles embedded in polyvinylpyrrolidone (PVP) environment under high-energy ball milling, an alternative algorithm to parameterize these structural imperfections is justified. Interfacial free-volume voids between neighboring nanoparticles filled with loosely packed As4S4 crystallites are considered as the most probable positron trapping sites. The observed variations in mixed positron–Ps trapping modes under nanostructurization are adequately defined with respect to the chemistry of guest nanoparticles. Direct evidence for this algorithm is provided as the basis of experimental three-term decomposed positron lifetime spectra for As4S4–PVP nanocomposites parameterized with respect to different fitting protocols.

  • characterization of radiation induced effects in amorphous Arsenic Sulfides by positron annihilation lifetime spectroscopy
    Journal of Materials Research, 2015
    Co-Authors: M Shpotyuk, A Ingram, O Shpotyuk
    Abstract:

    Positron annihilation lifetime spectroscopy is used to study the structural changes in amorphous Arsenic Sulfides of a binary As–S system induced by high-energy γ-radiation of 60 Co source. It is demonstrated that radiation-induced effects in positron trapping modes of the studied glasses are in strict correlation with shift of their fundamental optical absorption edge. The γ-induced physical aging is shown to be dominated in the rejuvenated S-rich glasses, thermally induced physical aging accompanies annealing of the rejuvenated g-As x S 100− x , while coordination topological defects are character for near-stoichiometric glasses (both annealed and rejuvenated). The competitive processes of free-volume void evolutions such as agglomeration–fragmentation, expansion–contraction, and charging–discharging are considered as possible stages of radiation- and thermally induced structural transformations. The meaningful model for γ-irradiation and relaxation-driven evolution in the void structure of As–S glasses is proposed. The free-volume evolution in g-As x S 100− x associated with thermally and γ-induced physical aging is shown to be consistent with a void fragmentation process, while the formation of γ-induced coordination topological defects leads mainly to void charging.