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  • 04. Solid Earth::04.08. Volcanology::04.08.01. Gases  (5)
  • Theoretical, Physical and Computational Chemistry  (5)
  • crystal structure  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Ionic vibrational breathing mode of metallic clusters (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 61 (1997), S. 613-626 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The energy of the vibrational mode with spherical symmetry, in which the ionic cores oscillate in the radial direction around the equilibrium geometry (ionic breathing mode) is calculated for trivalent (AlN, 2≤N≤50) and monovalent (NaN, 2≤N≤73; CsN, 2≤N≤74) metallic clusters. The ground-state total energy is calculated using density functional theory, with a spherically averaged pseudopotential to describe the ion-electron interaction and optimizing the geometry by the simulated annealing technique. The energy of the ionic mode is calculated by diagonalization of the dynamical matrix including the electronic relaxation in the linear response approximation. The compressibility and bulk modulus of the metallic cluster are obtained from the energies of the monopole oscillations. These energies present a linear behavior on the inverse of the cluster radius, which is analyzed using a semiclassical liquid drop mass formula for the total energy of the clusters and a scaling model. The values of the vibrational frequencies present electronic shell closing effects for the three metals.©1997 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Mixed lead-alkali clusters in the gas phase and in liquid alloys (1998)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 69 (1998), S. 341-348 
    Details
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio density functional calculations for NanPb, LinPb, NanPb4, and LinPb4 are reported. The abundance of Na6Pb observed in gas-phase experiments is explained as a consequence of evaporative cooling, which stops at Na6Pb because of the high evaporation energy of this cluster. Insight is also provided into the clustering in the liquid Li-Pb and Na-Pb alloys. Anomalies in several electronic, structural, and thermodynamic properties were detected at certain compositions (20% Pb in Li-Pb; 20% Pb and 50% Pb in Na-Pb) and our calculations support the interpretation of those anomalies in terms of the formation of octet and Zintl clusters.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 69: 341-348, 1998
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Crystal Structure of a New Acentric Oxide Fluoride of VIV: BaVOF4 (1994)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 620 (1994), S. 309-312 
    Details
    ISSN: 0044-2313
    Keywords: Barium vanadium oxide fluoride ; synthesis ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Kristallstruktur eines neuen azentrischen Oxidfluorids des VIV: BaVOF4Die Struktur von BaVOF4, erhalten durch hydrothermale Synthese, wurde röntgendiffraktometrisch aus Einkristalldaten bestimmt: Raumgruppe Fdd2 (azentrisch), Z = 16, a = 7,920(1), b = 27,608(2), c = 7,375(1) Å mit R = 0,0262, Rw = 0,0273 für 1 508 unabhängige Reflexe und 64 Parameter. Das Gitter wird von cis-verknüpften VOF5-Oktaedern aus gewinkelten unendlichen Ketten entlang [101] und [101] gebildet, die über Barium-Kationen verbunden sind. Die Lage der O2- und F- wird mittels Valenzband-Rechnungen diskutiert. Wie für BaTiOF4 und einige Verbindungen aus der Reihe AIIMIIIF5 (A = Ba, Sr und M = Ga, Al, Mn) kann die Struktur durch quasi-hexagonal dichteste Ebenen aus Stapeln von Ba2+, O2-- und F--Ionen beschrieben werden.
    Notes: The structure of BaVOF4 has been determined by X-ray diffraction data from a single crystal obtained by hydrothermal synthesis: S.G. Fdd2 (acentric), Z = 16, a = 7.920(1), b = 27.608(2) and c = 7.375(1) Å with R = 0.0262 and Rw = 0.0273 for 1 508 independent reflections and 64 parameters. The network is built up from cis-linked VOF5 octahedra forming infinite kinked chains running along the [101] and [101] directions, connected by barium cations. The location of O2- and F- ions is discussed using bond valence calculations. As for BaTiOF4 and some compounds in the series AIIMIIIF5 (A = Ba, Sr and M = Ga, Al, Mn), the structure can be described in terms of a quasi hexagonal compact planes stacking of Ba2+, O2- and F- ions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19946200216
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  • 4
    Electronic Resource
    Electronic Resource
    Ba7Fe6F32 · 2H2O: Original isolated trimers [Fe3F16]7- in a new defective jarlite-type compound (1995)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 621 (1995), S. 1025-1032 
    Details
    ISSN: 0044-2313
    Keywords: Barium iron fluoride ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Ba7Fe6F32 · 2H2O: isolierte [Fe3F16]7--Trimere in einer neuen Verbindung vom Defekt-Jarlit-TypBa7Fe6F32 · 2H2O wurde aus wäßriger HF-Lösung in einer Teflon-Bombe (Berghof) bei 180°C dargestellt. Ein teilweiser F-/OH--Austausch erfolgt in verdünnterem HF-Medium und führt zu Ba7Fe6F32-x(OH)x · 2H2O. Die Verbindungen kristallisieren im monoklinen System, Raumgruppe C2/m (Z = 2) mit a = 17,023(1) Å, b = 11,482(1) Å, c = 7,624(1) Å, β = 101,13(1)° für x = 0 und a = 17,036(2) Å, b = 11,489(1) Å, c = 7,620(2) Å, β = 101,48(1)° für x ≍ 5,3. Die Struktur wurde aus 2 256 bzw. 1 343 unabhängigen Reflexen für x = 0 bzw. x ≍ 5,3 mit einem Siemens AED2 Vierkreisdiffraktometer (MoKα) bestimmt; für x = 0: R = 0,0235, Rw = 0,0240; für x ≍ 5,3: R = 0,0324, Rw = 0,0335. Die eng mit dem Jarlit-Typ verwandte Struktur wird aus isolierten Oktaedertrimeren [Fe3F16]7- aufgebaut, die durch Ba2+-Ionen verknüpft werden. Die Lage der Anionen und Wassermoleküle wird mittels Valenzband-Rechnungen diskutiert. Magnetische-und Mössbauer-Untersuchungen werden diskutiert.
    Notes: Ba7Fe6F32 · 2H2O was prepared from HF aqueous solution in a teflon bomb (Berghof) at 180°C. A partial exchange F-/OH- can be realized in more diluted HF medium and leads to Ba7Fe6F32-x(OH)x · 2H2O. The compounds crystallize in the monoclinic system, space group C2/m (Z = 2) with a = 17.023(1) Å, b = 11.482(1) Å, c = 7.624(1) Å, β = 101.13(1)° for x = 0 and a = 17.036(2) Å, b = 11.489(1) Å, c = 7.620(2) Å, β = 101.48(1)° for x ≍ 5.3. The structures were determined from 2 256 and 1 343 independent reflections for x = 0 and x ≍ 5.3 respectively, collected with a Siemens AED2 four-circle diffractometer with the MoKα radiation (R = 0.0235 and Rw = 0.0240 for x = 0 and R = 0.0324 and Rw = 0.0335 for x ≍ 5.3). The structure, closely related to that of the Jarlite-type, is built up from isolated octahedra trimers [Fe3F16]7-, connected together by Ba2+-cations. The location of anions and water molecules is discussed from bond valence calculations. Magnetic and Mössbauer studies are reported and discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19956210622
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis and Crystal Structure of Ba4Mo2O5F7(HF2)3 · H2O (1997)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 439-443 
    Details
    ISSN: 0044-2313
    Keywords: Barium ; molybdenum oxyfluoride ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthese und Kristallstruktur von Ba4Mo2O5F7(HF2)3 · H2OEinkristalle von Ba4Mo2O5F7(HF2)3 · H2O wurden durch hydrothermale Synthese erhalten. Die Röntgenstrukturbestimmung ergab: Raumgruppe Pnnm, Z = 4, a = 16,497(1), b = 8,6939(5), c = 11,5174(6) Å (R = 0,0295, Rw = 0,0354 für 2425 unabhängige Reflexe und 126 Parameter). Mo ist im MoO3F3 verzerrt oktaedrisch umgeben. Zwei Oktaeder bilden, übereck verbunden durch O2-, (Mo2O5F6)4--Einheiten entlang der c-Achse. Die Ba-Atome liegen in zwei unterschiedlichen Umgebungen vor: einem quasi dreifach bekappten Kubus für Ba1 und Ba3 und einem dreifach bekappten trigonalen Prisma für Ba2.
    Notes: Single crystals of Ba4Mo2O5F7(HF2)3 · H2O are grown by hydrothermal synthesis. The structure is determined from X-Ray diffraction data: space group Pnnm, Z = 4, a = 16.497(1) Å, b = 8.6939(5) Å, c = 11.5174(6) Å (R = 0.0295, Rw = 0.0354 for 2425 independent reflections and 126 adjustable parameters). Mo atoms are in a distorted octahedral environment MoO3F3; two octahedra are linked by one O2- corner forming (Mo2O5F6)4- units lying along the c axis. Ba atoms present two kinds of environment: a quasi tricapped cube for Ba1 and Ba3 and a tricapped tricapped trigonal prism for Ba2.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19976230170
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  • 6
    Electronic Resource
    Electronic Resource
    A coupled density functional-molecular mechanics Monte Carlo simulation method: The water molecule in liquid water (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 17 (1996), S. 19-29 
    Details
    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A theoretical model to investigate chemical processes in solution is described. It is based on the use of a coupled density functional/molecular mechanics Hamiltonian. The most interesting feature of the method is that it allows a detailed study of the solute's electronic distribution and of its fluctuations. We present the results for isothermal-isobaric constant-NPT Monte Carlo simulation of a water molecule in liquid water. The quantum subsystem is described using a double-zeta quality basis set with polarization orbitals and nonlocal exchange-correlation corrections. The classical system is constituted by 128 classical TIP3P or Simple Point Charge (SPC) water molecules. The atom-atom radial distribution functions present a good agreement with the experimental curves. Differences with respect to the classical simulation are discussed. The instantaneous and the averaged polarization of the quantum molecule are also analyzed. © 1996 by John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Influence of environment on proton-transfer mechanisms in model triads from theoretical calculations (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 19 (1998), S. 1675-1688 
    Details
    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: We have carried out theoretical calculations to analyze molecular interactions and proton transfer mechanisms in the formate-imidazole-water system, which may be considered the simplest model of catalytic triads in serine proteases. Computations were carried out at the density functional theory level. The effect of a dielectric environment on energy surfaces is considered using a polarizable continuum model and the self-consistent reaction field approach. The role played by inertial and noninertial polarization of this environment is emphasized. Nonequilibrium solvation effects have been estimated. The results show that there are different reaction mechanisms, concerted or stepwise, that may be competitive, depending on the nature of the molecular environment.   © 1998 John Wiley & Sons, Inc.   J Comput Chem 19: 1675-1688, 1998
    Additional Material: 8 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Theoretical study of ester enolate-imine condensation route to β-lactams (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 19 (1998), S. 1826-1833 
    Details
    ISSN: 0192-8651
    Keywords: quantum-chemical computations ; β-lactams ; ester enolate-imine condensation ; solvent effect ; stepwise process ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The condensation reaction of the enolate of methyl acetate with formaldimine to afford a β-lactam was studied using the MP2-FC/6-31+G* level of theory taking into account the electrostatic effect of the solvent by means of a self-consistent reaction field continuum model. The reaction is a stepwise process with three main steps: the formation of the C3(SINGLE BOND)C4 bond, the closure of the β-lactam ring, and the elimination of the methoxide ion. The formation of the C3(SINGLE BOND)C4 bond is rate determining and according to our calculations is not a reversible step.   © 1998 John Wiley & Sons, Inc.   J Comput Chem 19: 1826-1833, 1998
    Additional Material: 4 Ill.
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  • 9
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    Combined monitoring of CO2 efflux, 222-Rn and 220-Rn in soil gas on Mt. Etna: a new geochemical tool for volcano surveillance. (2008)
    Details
    Publication Date: 2017-04-04
    Description: Since 2002, measurements of 222Rn, 220Rn activity and of CO2 efflux in soil and fumaroles were carried out at several locations on Mt. Etna volcano. An empirical relationship links the 222Rn/220Rn ratio to the CO2 efflux: deep sources of gas are characterized by high 222Rn activity and high CO2 efflux, whereas shallow sources are indicated by high 220Rn activity and relatively low CO2 efflux. This relationship is more constraining on the type and depth of the gas source than using the 222Rn/220Rn ratio alone. Since June 2006, periodical measurements of these parameters were carried out in 10 sites located over a surface of about 7 km2 on the east flank of Mt. Etna (Zafferana village). The chosen area is characterized by anomalous diffuse degassing produced by fault-driven leakage of volatiles from a magma source whose depth is inferred at about 4-7 km below the surface. The sampling frequency varied between once a month to once every ten days. We studied the temporal variation of the ratio between CO2 efflux and (222Rn/220Rn), that we define as a Soil Gas Disequilibrium Index (SGDI). Increases of this parameter occurred just before and during the 2006 eruptive period (July to December 2006), and at the onset of the March-May 2007 sequence of summit paroxysmal episodes. Furthermore, a slow increasing trend preceded by a few months the August-September 2007 summit activity of Etna, culminated with the September 4th 2007 paroxysmal episode. Remarkable spike-like increases not associated with eruptions occurred on January 10th, 2007, correlated with anomalous increases in volcanic tremor, and on June 20th, 2007, linked with marked short-lived anomalies both in the ground deformation and in the gravimetric signals recorded by the INGV-Catania monitoring networks. The last increase in this geochemical index was recorded in late March 2008, correlated with a marked increase both in the volcanic tremor and in the plume SO2 flux. This index looks very promising as a new tool for volcano monitoring, as it seem very sensitive to volcanic unrest.
    Description: Ministry for Foreign Affairs, Iceland Samorka – Icelandic Energy and Utilities University of Iceland The Icelandic Institute of Natural History Icelandic Road Administration Icelandic Meteorological Office Iceland GeoSurvey Viðlagatrygging Íslands Soil Conservation Service of Iceland Ministry for the Environment Ministry of Education, Science and Culture
    Description: Published
    Description: Reykjavík, Iceland
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: open
    Keywords: Mt. Etna ; soil CO2 efflux ; soil gas radon ; soil gas thoron ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Conference paper
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  • 10
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    Degassing behavior of Mt. Etna volcano (Italy) during 2007-2008, inferred (2010)
    EGU
    Details
    Publication Date: 2017-04-04
    Description: Studies on volcanic degassing have recently shown the important role of volatile release from active volcanoes in understanding magmatic processes prior to eruptions. Here we present and discuss the evolution of magmatic degassing that preceded and accompanied the 2008 Mt. Etna eruption. We tracked the ascent of magma bodies by high-temporal resolution measurements of SO2 emission rates and discrete sampling of SO2/HCl and SO2/HF molar ratios in the crater plume, as well as by periodic measurement of soil CO2 emission rates. Our data suggest that the first signs of upward migration of gas-rich magma before the 2008 eruption were observed in June 2007, indicated by a strong increase in soil CO2 efflux followed by a slow declining trend in SO2 flux and halogens. This degassing behavior preceded the mid-August 2007 summit activity culminated with the September 4th paroxysmal event. Five months later, a new increase in both soil CO2 and SO2 emission rates occurred before the November 23rd paroxysm, to drop down in late December. In the following months, geochemical parameters showed high variability, characterized by isolated sudden increases occurred in early December 2007 and late March 2008. In early May soil CO2, SO2 emission rates and S/Cl molar ratio gradually increased. Crater degassing peaked on May 13th marking the onset of the eruption. Eruptive activity was accompanied by a general steady-state of SO2 flux characterized by two main degassing cycles. These cycles preceded explosive activity at the eruptive vents, indicating terminal new-arrival of deep gas-rich magma bodies in the shallow plumbing system of Mt Etna. Conversely, halogens described a slight increasing trend till the end of 2008. These observations suggest an impulsive syn-eruptive dynamics of magma transfer from depth to the surface. Differently from the SO2 emission rates, the S/Cl ratio and the soil CO2 efflux values showed an increasing trend from mid-April to mid-July 2008, indicating steady-increasing input of deeper, gas-rich magma. Since August, geochemical parameters decreased, suggesting that new magma has not arrived from depth. According to our interpretation, both the CO2 efflux and the S/Cl ratio increases observed in early November may indicate a new input of fresh magma form depth. Finally, the estimated volume of degassing magma showed substantial equilibrium between degassed and erupted magma suggesting an “eruptive” steady-state of the volcano.
    Description: INGV, Sezione di Catania; INGV, Sezione di Pisa; University of Cambridge, Cambridge, UK
    Description: Published
    Description: Vienna, Austria
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: open
    Keywords: Mt. Etna ; plume gases ; soil CO2 ; eruption ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Abstract
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