Thermal behavior of realgar As4S4, and of arsenolite As2O3 and non-stoichiometric As8S8+x crystals produced from As4S4 melt recrystallization
-
Paolo Ballirano
Abstract
An in situ high-temperature X-ray powder diffraction study of the thermal behavior of realgar (α-As4S4) has been carried out. Data, measured in transmission geometry on a non-hermetically sealed capillary, indicate that the realgar → β-As4S4 phase transition starts at 558 K and is completed at 573 K due to kinetics. Melting starts at 578 K and is completed at 588 K. Thermal expansion of realgar is significant and fairly isotropic. In fact, the a- and b-parameters expand almost at the same rate, whereas the c-parameter is slightly softer against heating. Moreover, the β-angle contracts as temperature is raised. The geometry of the As4S4 molecule is largely independent from heating. The lengthening of a few As-S and As-As contacts above or near the sum of the As,S van der Waals radii represents the driving force of the phase transition. In addition, the thermal behavior of arsenolite As2O3 and nonstoichiometric As8S8+x crystals produced from As4S4 melt recrystallization has been investigated. Two members located along the β-As4S4-alacranite (As8S9) series joint were identified at RT: a term close to the β-As4S4 end-member (As8S8+x+x: x = ca. 0.1) and one term of approximate As8S8.3 composition. The thermal expansion of β-As4S4 is significantly anisotropic following the αb > αa > αc relationship. This is clearly the result of the different packing scheme of the As4S4 cages in β-As4S4 with respect to realgar. The dependence of cell parameters and volume of As8S8.3 is more complicated. In fact, a strong discontinuity on the dependence of cell parameters and volume is observed in the 403-443 K thermal range, i.e., that at which As8S8.3 converts partly to realgar. A significant volume expansion is observed as a result of a change of composition to As8S8.7.
© 2015 by Walter de Gruyter Berlin/Boston
Artikel in diesem Heft
- Actinides in Geology, Energy, and the Environment. Petrography and geochronology of the Pele Mountain quartz-pebble conglomerate uranium deposit, Elliot Lake District, Canada
- Celadonite in continental flood basalts of the Columbia River Basalt Group
- Thermodynamics of manganese oxides: Effects of particle size and hydration on oxidation-reduction equilibria among hausmannite, bixbyite, and pyrolusite
- Grossular: A crystal-chemical, calorimetric, and thermodynamic study
- Redetermination of high-temperature heat capacity of Mg2SiO4 ringwoodite: Measurement and lattice vibrational model calculation
- Thermal behavior of realgar As4S4, and of arsenolite As2O3 and non-stoichiometric As8S8+x crystals produced from As4S4 melt recrystallization
- Thermodynamics of the magnetite-ulvöspinel (Fe3O4-Fe2TiO4) solid solution
- Raman spectroscopy of (Ca,Mg)MgSi2O6 clinopyroxenes
- In-situ Raman spectroscopic study of sulfur speciation in oxidized magmatic-hydrothermal fluids
- Structural anisotropy and annealing-induced nanoscale atomic rearrangements in metamict titanite
- Hydrous fluid as the growth media of natural polycrystalline diamond, carbonado: Implication from IR spectra and microtextural observations
- Metastable equilibrium in the C-H-O system: Graphite deposition in crustal fluids
- Controlled morphogenesis of amorphous silica and its relevance to biosilicification
- Structural relaxation in tetrahedrally coordinated Co2+ along the gahnite-Co-aluminate spinel solid solution
- Limitations of Fe2+ and Mn2+ site occupancy in tourmaline: Evidence from Fe2+- and Mn2+-rich tourmaline
- Isothermal compression of face-centered cubic iron
- Bonding and structural changes in siderite at high pressure
- Energetics and kinetics of carbonate orientational ordering in vaterite calcium carbonate
- Growth process and crystallographic properties of ammonia-induced vaterite
- Argesite, (NH4)7Bi3Cl16, a new mineral from La Fossa Crater, Vulcano, Aeolian Islands, Italy: A first example of the [Bi2Cl10]4− anion
- Experimental study of mineral equilibria in the system K2O(Li2O)-Al2O3-SiO2-H2O-HF at 300 to 600 °C and 100 MPa with application to natural greisen systems
- Tobelite and NH+4-rich muscovite single crystals from Ordovician Armorican sandstones (Brittany, France): Structure and crystal chemistry
- The enigmatic iron oxyhydroxysulfate nanomineral schwertmannite: Morphology, structure, and composition
- Ferric iron and water incorporation in wadsleyite under hydrous and oxidizing conditions: A XANES, Mössbauer, and SIMS study
- Kircherite, a new mineral of the cancrinite-sodalite group with a 36-layer stacking sequence: Occurrence and crystal structure
- Molecular models of birnessite and related hydrated layered minerals
- Letter: Gold-telluride nanoparticles revealed in arsenic-free pyrite
- Letter: XAS evidence for the stability of polytellurides in hydrothermal fluids up to 599 °C, 800 bar
Artikel in diesem Heft
- Actinides in Geology, Energy, and the Environment. Petrography and geochronology of the Pele Mountain quartz-pebble conglomerate uranium deposit, Elliot Lake District, Canada
- Celadonite in continental flood basalts of the Columbia River Basalt Group
- Thermodynamics of manganese oxides: Effects of particle size and hydration on oxidation-reduction equilibria among hausmannite, bixbyite, and pyrolusite
- Grossular: A crystal-chemical, calorimetric, and thermodynamic study
- Redetermination of high-temperature heat capacity of Mg2SiO4 ringwoodite: Measurement and lattice vibrational model calculation
- Thermal behavior of realgar As4S4, and of arsenolite As2O3 and non-stoichiometric As8S8+x crystals produced from As4S4 melt recrystallization
- Thermodynamics of the magnetite-ulvöspinel (Fe3O4-Fe2TiO4) solid solution
- Raman spectroscopy of (Ca,Mg)MgSi2O6 clinopyroxenes
- In-situ Raman spectroscopic study of sulfur speciation in oxidized magmatic-hydrothermal fluids
- Structural anisotropy and annealing-induced nanoscale atomic rearrangements in metamict titanite
- Hydrous fluid as the growth media of natural polycrystalline diamond, carbonado: Implication from IR spectra and microtextural observations
- Metastable equilibrium in the C-H-O system: Graphite deposition in crustal fluids
- Controlled morphogenesis of amorphous silica and its relevance to biosilicification
- Structural relaxation in tetrahedrally coordinated Co2+ along the gahnite-Co-aluminate spinel solid solution
- Limitations of Fe2+ and Mn2+ site occupancy in tourmaline: Evidence from Fe2+- and Mn2+-rich tourmaline
- Isothermal compression of face-centered cubic iron
- Bonding and structural changes in siderite at high pressure
- Energetics and kinetics of carbonate orientational ordering in vaterite calcium carbonate
- Growth process and crystallographic properties of ammonia-induced vaterite
- Argesite, (NH4)7Bi3Cl16, a new mineral from La Fossa Crater, Vulcano, Aeolian Islands, Italy: A first example of the [Bi2Cl10]4− anion
- Experimental study of mineral equilibria in the system K2O(Li2O)-Al2O3-SiO2-H2O-HF at 300 to 600 °C and 100 MPa with application to natural greisen systems
- Tobelite and NH+4-rich muscovite single crystals from Ordovician Armorican sandstones (Brittany, France): Structure and crystal chemistry
- The enigmatic iron oxyhydroxysulfate nanomineral schwertmannite: Morphology, structure, and composition
- Ferric iron and water incorporation in wadsleyite under hydrous and oxidizing conditions: A XANES, Mössbauer, and SIMS study
- Kircherite, a new mineral of the cancrinite-sodalite group with a 36-layer stacking sequence: Occurrence and crystal structure
- Molecular models of birnessite and related hydrated layered minerals
- Letter: Gold-telluride nanoparticles revealed in arsenic-free pyrite
- Letter: XAS evidence for the stability of polytellurides in hydrothermal fluids up to 599 °C, 800 bar
