Abstract
Using the hybrid B3LYP density functional method, we computed the ab initio thermodynamic and thermophysical properties of two sapphirine end-members, Mg4Al8Si2O20 (sapphirine-442) and Mg3Al10SiO20 (sapphirine-351), in the join Mg3(Mg1-XAlX)Al8(AlXSi1-X)SiO20 with X = 0-1. Static and vibrational calculations performed in the framework of the quasi-harmonic approximation allowed to define the equation of state (EOS), elastic constant tensor, seismic velocities, IR spectra, mode Grüneisen parameters, and thermodynamic properties of both sapphirine end-members. A modified Kieffer’s model was adopted to evaluate the optic and acoustic mode contributions to thermodynamic functions stemming from ab initio phonon frequencies and directionally averaged seismic velocities, respectively. The extrinsic stability and liquidus phase relations of sapphirine were investigated in the model system MgO-Al2O3-SiO2 (MAS) at different pressure conditions by coupling first-principles calculations with the hybrid polymeric approach (HPA) for multicomponent liquids and minimizing the Gibbs free energy of liquid and solid phases through the convex-hull analysis of equipotential surfaces. According to our thermodynamic modeling, sapphirine turns out to have a small field of primary crystallization in the MAS ternary diagram at 1-bar pressure, which becomes larger due to pressure effects up to 10 kbar, then progressively shrinks and disappears above 21 kbar.
© 2014 by Walter de Gruyter Berlin/Boston
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Artikel in diesem Heft
- Highlights and Breakthroughs
- An alternative to alteration and melting processes in the Earth: Reaction between hydrogen (H2) and oxide components in the Earth in space and time
- The crystallographic and petrogenetic significance of pegmatite phosphates
- Small grains and big implications: Accessory Ti- and Zr-minerals as petrogenetic indicators in HP and UHP marbles
- What Lurks in the Martian Rocks and Soil? Investigations of Sulfates, Phosphates, and Perchlorates
- Natural Fe-bearing oxides and sulfates from the Rio Tinto Mars analog site: Critical assessment of VNIR reflectance spectroscopy, laser Raman spectroscopy, and XRD as mineral identification tools
- Dissolution rates of amorphous Al- and Fe-phosphates and their relevance to phosphate mobility on Mars
- Stability and spectroscopy of Mg sulfate minerals: Role of hydration on sulfur isotope partitioning
- Synthesis and characterization of the Mars-relevant phosphate minerals Fe- and Mg-whitlockite and merrillite and a possible mechanism that maintains charge balance during whitlockite to merrillite transformation
- Minerals in the Human Body
- Determination of the concentration of asbestos minerals in highly contaminated mine tailings: An example from abandoned mine waste of Crètaz and Èmarese (Valle d’Aosta, Italy)
- Spinels Renaissance: The past, present, and future of those ubiquitous minerals and materials
- Pressure-volume equation of state for chromite and magnesiochromite: A single-crystal X-ray diffraction investigation
- The systematics of the spinel-type minerals: An overview
- Chemistry and Mineralogy of Earth’s Mantle
- Formation of SiH4 and H2O by the dissolution of quartz in H2 fluid under high pressure and temperature
- Identifying the spin transition in Fe2+-rich MgSiO3 perovskite from X-ray diffraction and vibrational spectroscopy
- Mantle-derived guyanaite in a Cr-omphacitite xenolith from Moses Rock diatreme, Utah
- Pluton assembly and the genesis of granitic magmas: Insights from the GIC pluton in cross section, Sierra Nevada Batholith, California
- First-principles molecular dynamics simulations of MgSiO3 glass: Structure, density, and elasticity at high pressure
- A new UHP metamorphic complex in the ~1.8 Ga Nagssugtoqidian Orogen of West Greenland
- Visible and short-wave infrared reflectance spectroscopy of REE fluorocarbonates
- Volatile abundances of coexisting merrillite and apatite in the martian meteorite Shergotty: Implications for merrillite in hydrous magmas
- Sb5+ and Sb3+ substitution in segnitite: A new sink for As and Sb in the environment and implications for acid mine drainage
- First-principles elasticity of monocarboaluminate hydrates
- Substitution of Ti3+ and Ti4+ in hibonite (CaAl12O19)
- Exploring the effect of lithium on pegmatitic textures: An experimental study
- XANES measurements of Cr valence in olivine and their applications to planetary basalts
- Z-contrast imaging and ab initio study on “d” superstructure in sedimentary dolomite
- Influence of temperature, pressure, and chemical composition on the electrical conductivity of granite
- Ti- and Zr-minerals in calcite-dolomite marbles from the ultrahigh-pressure Kimi Complex, Rhodope mountains, Greece: Implications for the P-T evolution based on reaction textures, petrogenetic grids, and geothermobarometry
- Ab initio thermodynamic and thermophysical properties of sapphirine end-members in the join Mg4Al8Si2O20-Mg3Al10SiO20
- The relation between Li ↔ Na substitution and hydrogen bonding in five-periodic singlechain silicates nambulite and marsturite: A single-crystal X-ray study
- Natural analogs of belite sulfoaluminate cement clinkers from Negev Desert, Israel
- Australian sedimentary opal-A and its associated minerals: Implications for natural silica sphere formation
- The 2H and 3R polytypes of sabieite, NH4Fe3+(SO4)2, from a natural fire in an oil-bearing shale near Milan, Ohio
- Letter
- Te-rich raspite, Pb(W0.56Te0.44)O4, from Tombstone, Arizona, U.S.A.: The first natural example of Te6+ substitution for W6+
- New Mineral Names
- Book Review