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Giovanni Valdre - One of the best experts on this subject based on the ideXlab platform.
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infrared and raman spectroscopic features of Clinochlore mg6si4o10 oh 8 a density functional theory contribution
Applied Clay Science, 2020Co-Authors: Gianfranco Ulian, Daniele Moro, Giovanni ValdreAbstract:Abstract Mineral identification and analysis are often performed by using vibrational spectroscopies, namely infrared and Raman techniques. However, very few spectroscopy data are available on Clinochlore, an important phyllosilicate with manifold applications in several fields. In the present work, ab initio Density Functional Theory simulation was employed to calculate the infrared and Raman spectra at Γ points and the phonon dispersion at different k-points of the magnesium end-member of Clinochlore, with ideal chemical formula Mg6Si4O10(OH)8 and space group C2/m. Each phonon mode of the mineral was assigned to specific vibrations of the ionic groups in the structure. The theoretical results were found in good agreement with the available experimental data in literature, further extending the knowledge on the vibrational properties of Clinochlore, which could be useful for experimental characterization of this mineral phase in various and different fields of research.
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simulated infrared and raman spectroscopy complex dielectric function and refractive index dataset of monoclinic c2 m stoichiometric Clinochlore mg6si4o10 oh 8 as obtained from density functional theory
Data in Brief, 2020Co-Authors: Gianfranco Ulian, Daniele Moro, Giovanni ValdreAbstract:This article reports a simulated dataset of the vibrational (infrared and Raman) and optical properties (complex dielectric function and refractive index) of Clinochlore, an important mineral belonging to the phyllosilicate family [1]. The data here reported were calculated from ab initio Density Functional Theory (DFT) simulations at B3LYP level, including a correction for the dispersive forces (B3LYP-D* approach) and all-electron Gaussian-type orbitals basis sets. This dataset was calculated between 0 cm-1 and 4000 cm-1 and comprises infrared, reflectance and Raman spectra, frequency-dependent complex dielectric function and complex refractive index of Clinochlore. The data was validated against available experimental spectroscopic results reported in literature and can be of help in several application fields, for instance fundamental georesource exploration and exploitation, in applied mineralogy, geology, material science, and as a reference to assess the quality of other theoretical approaches.
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3d meso nanostructures in cleaved and nanolithographed mg al hydroxysilicate Clinochlore topology crystal chemistry and surface properties
Applied Clay Science, 2019Co-Authors: Daniele Moro, Gianfranco Ulian, Giovanni ValdreAbstract:Abstract The peculiar physico-chemical properties that a solid surface can present, unlike the bulk, are the key for a huge amount of important and widespread processes, including for instance, contaminant and biomolecules adsorption, solid-state and ion exchange reactions, soil aggregation, adhesion in micro and nanodevices. In this regard, the development of new materials and three-dimensional nanofabrication technologies becomes a fundamental challenge. Here, the authors present both natural and synthetic three-dimensional meso-nanostructures of a particular Mg-Al-hydroxysilicate (mineral Clinochlore) produced by scanning probe microscopy related methods. Topology, crystal-chemistry, and surface properties were addressed by experimental and theoretical methodologies on nanocleaved and nanolithographed Clinochlore. Scanning probe microscopy revealed a meso-nanostructured heterogeneous surface in terms of morphology, hydrophilic/phobic character and surface potential. The possibility to arbitrarily tailor and fabricate surface nanopatterns by SPM-based nanolithography is reported. Quantum mechanical simulations of the crystal-chemical structure and material properties supported and corroborated the experimental data. These findings suggest that the heterogeneous three-dimensional meso-nanostructured surface of Clinochlore can represent an optimal effective substrate for exploring specific and innovative catalytic, electrochemical and biological processes at the nanoscale.
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first principle investigation of the mechanical properties of natural layered nanocomposite Clinochlore as a model system for heterodesmic structures
Composite Structures, 2018Co-Authors: Gianfranco Ulian, Daniele Moro, Giovanni ValdreAbstract:Abstract For many technological applications, it is of paramount importance to study the mechanical behaviour of heterogeneous multi layered materials , and how they develop at the nanoscale . By employing a nature-based approach ( learning from Nature) and ab initio Density Functional Theory (DFT) methods, in the present work we report a detailed mechanical investigation of a very interesting natural heterodesmic nanocomposite material made of alternated stacked magnesium hydroxide (brucite-like) and hydroxysilicate (talc-like) layers. This mineral phase has very interesting surface and bulk crystal-chemical properties, but its elastic behaviour is still not well known. Both the hydrostatic compression and the second order elastic constants were reported. An ideal, stoichiometric structure and a cation-substituted one were considered to stress the power of DFT methods in tailoring the properties, and the results were presented and consistently discussed with the experimental data available in literature. This study showed that the DFT/B3LYP-D∗ approach represents a powerful route to investigate other layered structures of multilayer composites for tailoring of specific mechanical properties.
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zeolitic type bronsted lowry sites distribution imaged on Clinochlore
American Mineralogist, 2011Co-Authors: Giovanni Valdre, Sergio Tosoni, Daniele MoroAbstract:Although Bronsted-Lowry (B-L) sites in solids, such as zeolites, have been studied extensively, all previous investigations were conducted on a bulk (average) basis. In contrast, the imaging and distribution of B-L sites on atomic flat Al-rich chlorite are presented by using Scanning probe and Kelvin probe force microscopy. These techniques are used to correlate, at the nanoscale, the contrast due to the surface potential (related to the B-L proton) with the surface morphology and crystal chemistry. Quantum mechanical modeling (DFT) is consistent with the experimental results. Imaging of the distribution of B-L sites in solids and the existence of two-dimensional (2D) arrays of zeolitic-type B-L sites in chlorites is shown. The study demonstrates the general validity of the Bronsted-Lowry acid-base theory extended to pure solids without any solution medium. The experimental approach developed here can facilitate the search of B-L site architectures in minerals.
Pierre Lanari - One of the best experts on this subject based on the ideXlab platform.
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a thermodynamic model for di trioctahedral chlorite from experimental and natural data in the system mgo feo al2o3 sio2 h2o applications to p t sections and geothermometry
Contributions to Mineralogy and Petrology, 2014Co-Authors: Pierre Lanari, Thomas Wagne, Olivie VidalAbstract:We present a new thermodynamic activity-composition model for di-trioctahedral chlorite in the system FeO–MgO–Al2O3–SiO2–H2O that is based on the Holland–Powell internally consistent thermodynamic data set. The model is formulated in terms of four linearly independent end-members, which are amesite, Clinochlore, daphnite and sudoite. These account for the most important crystal-chemical substitutions in chlorite, the Fe–Mg, Tschermak and di-trioctahedral substitution. The ideal part of end-member activities is modeled with a mixing-on-site formalism, and non-ideality is described by a macroscopic symmetric (regular) formalism. The symmetric interaction parameters were calibrated using a set of 271 published chlorite analyses for which robust independent temperature estimates are available. In addition, adjustment of the standard state thermodynamic properties of sudoite was required to accurately reproduce experimental brackets involving sudoite. This new model was tested by calculating representative P–T sections for metasediments at low temperatures (<400 °C), in particular sudoite and chlorite bearing metapelites from Crete. Comparison between the calculated mineral assemblages and field data shows that the new model is able to predict the coexistence of chlorite and sudoite at low metamorphic temperatures. The predicted lower limit of the chloritoid stability field is also in better agreement with petrological observations. For practical applications to metamorphic and hydrothermal environments, two new semi-empirical chlorite geothermometers named Chl(1) and Chl(2) were calibrated based on the chlorite + quartz + water equilibrium (2 Clinochlore + 3 sudoite = 4 amesite + 4 H2O + 7 quartz). The Chl(1) thermometer requires knowledge of the (Fe3+/ΣFe) ratio in chlorite and predicts correct temperatures for a range of redox conditions. The Chl(2) geothermometer which assumes that all iron in chlorite is ferrous has been applied to partially recrystallized detrital chlorite from the Zone houillere in the French Western Alps.
Mark D. Welch - One of the best experts on this subject based on the ideXlab platform.
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novel high pressure behavior in chlorite a synchrotron xrd study of Clinochlore to 27 gpa
American Mineralogist, 2004Co-Authors: Mark D. Welch, Andrew P. Jephcoat, Annette K KleppeAbstract:The high-pressure behavior of synthetic end-member II b Clinochlore, Mg5Al(Si3Al)O10(OH)8, has been studied by synchrotron X-ray powder diffraction to 27 GPa at 300 K. A non-quenchable, reversible transformation occurs between 9 and 10 GPa that is dominated by compression normal to the structural layering and has an associated small but significant shear of the β angle from 97.2 to 96.3°. The high-pressure chlorite is more compressible than the low-pressure phase. Diffraction patterns of the high-pressure chlorite are very similar from 10 to 27 GPa, indicating that it persists stably with no significant change in β to very high pressures: β is effectively locked at the transformation to the high-pressure structure. It is proposed that the transformation is not polytypic and that the distortion reflects reorganization of the interlayer hydrogen bonding, possibly involving novel proton behavior as adjacent sheets of cations of the brucite-like and tetrahedral layers close down on the sheet of interlayer protons. The transformation is likely driven by O atom close-packing requirements imposed by pressure.
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The effect of pressure upon hydrogen bonding in chlorite: A Raman spectroscopic study of Clinochlore to 26.5 GPa
American Mineralogist, 2003Co-Authors: Annette K Kleppe, Andrew P. Jephcoat, Mark D. WelchAbstract:The effect of pressure upon hydrogen bonding in synthetic end-member Clinochlore, (Mg5Al)(Si3 Al)O10 (OH)8 , has been studied in situ by high-pressure micro-Raman spectroscopy in a moissanite-anvil cell to 26.5 GPa at 300 K. The ambient spectrum consists of three OH-stretching bands between 3400 and 3650 cm–1 , attributed to the hydrogen-bonded interlayer OH, and a narrow band at 3679 cm–1 that is assigned to the non-hydrogen-bonded OH groups of the talc-like 2:1 layer. The pressure dependence of the OH modes is linear up to 6 GPa. Near 9 GPa a major discontinuity occurs in the pressure dependence of the interlayer OH-stretching modes. It involves frequency increases >100 cm–1 that indicate major changes in hydrogen bonding. The OH mode of the 2:1 layer does not show discontinuous behavior at 9 GPa. A further discontinuity occurs at ~16 GPa. This discontinuity affects both interlayer and 2:1 OH, and is likely to be associated with a change in the overall compression mechanism of Clinochlore. The spectroscopic behavior is a completely re- versible function of pressure. Predictions based upon recent high-pressure diffraction studies of hydrogen bonding and compression of Clinochlore suggest that the 9 GPa transition is associated with attainment of an O2– -O2– -contact distance of 2.7 Å.
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compressibility of Clinochlore to 8 gpa at 298 k and a comparison with micas
European Journal of Mineralogy, 2002Co-Authors: Mark D. Welch, Wilson A CrichtonAbstract:The equation of state of deuterated synthetic end-member C 2/ m Clinochlore, Mg 5 Al(Si 3 Al)O 10 (OD) 8 , has been determined by synchrotron X-ray powder diffraction in the pressure range 0 - 7.7 GPa. The room-temperature bulk modulus K 0 obtained from a fit of sixteen measurements to a second-order Birch-Murnaghan equation of state ( K 0 ’ = 4) is K 0 = 81.0 ± 0.5 GPa. Fitting to a third-order Birch-Murnaghan equation of state gives K 0 = 83.1 ± 1.7 GPa and K 0 ’ = 3.3 ± 0.6 and, within error, the two fits are indistinguishable over this pressure range. Axial moduli ( K 0 ’ = 4) for Clinochlore are: K 0 a = 91(1) GPa, K 0b = 89(1) GPa, K 0 c =67(2) GPa. Comparison with published compressibilities for phlogopite, muscovite and phengite reveals that the micas are slightly less compressible along [100] and [010] than Clinochlore, but micas are three times more compressible than Clinochlore normal to the (001) structural layering. The very different compressibilities of micas and Clinochlore normal to their polyhedral sheets indicates that the type of interlayer bonding has a major effect upon compressibility.
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high pressure behavior of Clinochlore
American Mineralogist, 2001Co-Authors: Mark D. Welch, W G MarshallAbstract:The room-temperature bulk modulus of synthetic end-member Clinochlore, Mg5AlSi3AlO10(OD)8, has been determined in the pressure range 0 to 6.5 GPa using neutron powder diffraction: K = 75.4(2.7) GPa, K ′ = 4; K = 72.3(2.4) GPa, K ′ = 5.4(1.0). A structural comparison is made with the related mineral brucite, Mg(OH)2. Clinochlore is a much stiffer structure than brucite ( K = 41 – 47 GPa). Both minerals have very similar in-plane compressions of their polyhedral sheets and so their very different bulk moduli arise from different compressibilities normal to the structural layering. Rietveld refinements of neutron-diffraction data for Clinochlore collected at 0, 1.2, 2.5, and 4.7 GPa reveal that compression normal to the layering is equally partitioned between the interlayer and the 2:1 layer; the octahedral sheets of the brucite-like and 2:1 layers are uncompressed to 4.7 GPa. Increasing pressure strengthens the H3(D3)…O3 hydrogen bond, which contracts linearly from 1.88(2) A at 0 GPa to 1.77(2) A at 4.7 GPa, possibly with a concomitant lengthening of the O6-H3(D3) hydroxyl bond from 1.05(2) A to 1.10(2) A over the same pressure range.
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a multinuclear nmr study of Clinochlore
American Mineralogist, 1995Co-Authors: Mark D. Welch, Jamie Barras, Jacek KlinowskiAbstract:Tetrahedral and octahedral ordering in synthetic elinochlore with compositions (MgsAI)[Si3Al]OIO(OH). and (Mg...56AII.44)[Si2s.AI1.42]OIO(OH). have been studied by 29Si, 27 AI, and IH MAS NMR spectroscopy. The 29Sispectra indicate that AI-O-AI avoidance occurs on tetrahedral sites with considerable short-range order in accordance with the Homogeneous Dispersion of Charges (HOC) model of Herrero et ai. (1985a), in which charge imbalance within the tetrahedral sheets is minimized. The
Andrew P. Jephcoat - One of the best experts on this subject based on the ideXlab platform.
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novel high pressure behavior in chlorite a synchrotron xrd study of Clinochlore to 27 gpa
American Mineralogist, 2004Co-Authors: Mark D. Welch, Andrew P. Jephcoat, Annette K KleppeAbstract:The high-pressure behavior of synthetic end-member II b Clinochlore, Mg5Al(Si3Al)O10(OH)8, has been studied by synchrotron X-ray powder diffraction to 27 GPa at 300 K. A non-quenchable, reversible transformation occurs between 9 and 10 GPa that is dominated by compression normal to the structural layering and has an associated small but significant shear of the β angle from 97.2 to 96.3°. The high-pressure chlorite is more compressible than the low-pressure phase. Diffraction patterns of the high-pressure chlorite are very similar from 10 to 27 GPa, indicating that it persists stably with no significant change in β to very high pressures: β is effectively locked at the transformation to the high-pressure structure. It is proposed that the transformation is not polytypic and that the distortion reflects reorganization of the interlayer hydrogen bonding, possibly involving novel proton behavior as adjacent sheets of cations of the brucite-like and tetrahedral layers close down on the sheet of interlayer protons. The transformation is likely driven by O atom close-packing requirements imposed by pressure.
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The effect of pressure upon hydrogen bonding in chlorite: A Raman spectroscopic study of Clinochlore to 26.5 GPa
American Mineralogist, 2003Co-Authors: Annette K Kleppe, Andrew P. Jephcoat, Mark D. WelchAbstract:The effect of pressure upon hydrogen bonding in synthetic end-member Clinochlore, (Mg5Al)(Si3 Al)O10 (OH)8 , has been studied in situ by high-pressure micro-Raman spectroscopy in a moissanite-anvil cell to 26.5 GPa at 300 K. The ambient spectrum consists of three OH-stretching bands between 3400 and 3650 cm–1 , attributed to the hydrogen-bonded interlayer OH, and a narrow band at 3679 cm–1 that is assigned to the non-hydrogen-bonded OH groups of the talc-like 2:1 layer. The pressure dependence of the OH modes is linear up to 6 GPa. Near 9 GPa a major discontinuity occurs in the pressure dependence of the interlayer OH-stretching modes. It involves frequency increases >100 cm–1 that indicate major changes in hydrogen bonding. The OH mode of the 2:1 layer does not show discontinuous behavior at 9 GPa. A further discontinuity occurs at ~16 GPa. This discontinuity affects both interlayer and 2:1 OH, and is likely to be associated with a change in the overall compression mechanism of Clinochlore. The spectroscopic behavior is a completely re- versible function of pressure. Predictions based upon recent high-pressure diffraction studies of hydrogen bonding and compression of Clinochlore suggest that the 9 GPa transition is associated with attainment of an O2– -O2– -contact distance of 2.7 Å.
Olivie Vidal - One of the best experts on this subject based on the ideXlab platform.
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a thermodynamic model for di trioctahedral chlorite from experimental and natural data in the system mgo feo al2o3 sio2 h2o applications to p t sections and geothermometry
Contributions to Mineralogy and Petrology, 2014Co-Authors: Pierre Lanari, Thomas Wagne, Olivie VidalAbstract:We present a new thermodynamic activity-composition model for di-trioctahedral chlorite in the system FeO–MgO–Al2O3–SiO2–H2O that is based on the Holland–Powell internally consistent thermodynamic data set. The model is formulated in terms of four linearly independent end-members, which are amesite, Clinochlore, daphnite and sudoite. These account for the most important crystal-chemical substitutions in chlorite, the Fe–Mg, Tschermak and di-trioctahedral substitution. The ideal part of end-member activities is modeled with a mixing-on-site formalism, and non-ideality is described by a macroscopic symmetric (regular) formalism. The symmetric interaction parameters were calibrated using a set of 271 published chlorite analyses for which robust independent temperature estimates are available. In addition, adjustment of the standard state thermodynamic properties of sudoite was required to accurately reproduce experimental brackets involving sudoite. This new model was tested by calculating representative P–T sections for metasediments at low temperatures (<400 °C), in particular sudoite and chlorite bearing metapelites from Crete. Comparison between the calculated mineral assemblages and field data shows that the new model is able to predict the coexistence of chlorite and sudoite at low metamorphic temperatures. The predicted lower limit of the chloritoid stability field is also in better agreement with petrological observations. For practical applications to metamorphic and hydrothermal environments, two new semi-empirical chlorite geothermometers named Chl(1) and Chl(2) were calibrated based on the chlorite + quartz + water equilibrium (2 Clinochlore + 3 sudoite = 4 amesite + 4 H2O + 7 quartz). The Chl(1) thermometer requires knowledge of the (Fe3+/ΣFe) ratio in chlorite and predicts correct temperatures for a range of redox conditions. The Chl(2) geothermometer which assumes that all iron in chlorite is ferrous has been applied to partially recrystallized detrital chlorite from the Zone houillere in the French Western Alps.