Physics and Chemistry of Minerals
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Visualization-based analysis of structural and dynamical properties of simulated hydrous silicate melt
Physics and Chemistry of Minerals - Tập 37 - Trang 103-117 - 2009
We have explored first-principles molecular dynamics simulation data for hydrous MgSiO3 liquid (with 10 wt% water) to gain insight into its structural and dynamical behavior as a function of pressure (0–150 GPa) and temperature (2,000–6,000 K). By visualizing/analyzing a number of parameters associated with short- and mid-range orders, we have shown that the melt structure changes substantially on......
Biradical states of oxygen-vacancy defects in α-quartz: centers $$ E_{2}^{\prime \prime } $$ and $$ E_{4}^{\prime \prime } $$
Physics and Chemistry of Minerals - Tập 38 - Trang 647-654 - 2011
Several new radiation defects with total electron spin S = 1 occurring in electron-irradiated, synthetic α-quartz have been observed by using electron paramagnetic resonance spectroscopy. These defects are considered to be biradicals, i.e., pairs of S = 1/2 species. The concentration of these centers depends on the condition of the fast-electron irradiation. They have different decay behaviors tha......
Crystal structure and investigation of Bi2TeO6·nH2O (0 ≤ n ≤ $${\raise0.5ex\hbox{$\scriptstyle 2$} \kern-0.1em/\kern-0.15em \lower0.25ex\hbox{$\scriptstyle 3$}}$$ ): natural and synthetic montanite
Physics and Chemistry of Minerals - Tập 49 - Trang 1-16 - 2022
The crystal structure of montanite has been determined using single-crystal X-ray diffraction on a synthetic sample, supported by powder X-ray diffraction (PXRD), electron microprobe analysis (EPMA) and thermogravimetric analyses (TGA). Montanite was first described in 1868 as Bi2TeO6·nH2O (n = 1 or 2). The determination of the crystal structure of synthetic montanite (refined composition Bi2TeO6·......
First-principles-based calculations of the CaCO3–MgCO3 and CdCO3–MgCO3 subsolidus phase diagrams
Physics and Chemistry of Minerals - Tập 30 - Trang 88-97 - 2003
Planewave pseudopotential calculations of supercell total energies were used as bases for first-principles calculations of the CaCO3–MgCO3 and CdCO3–MgCO3 phase diagrams. Calculated phase diagrams are in qualitative to semiquantitative agreement with experiment. Two unobserved phases, Cd3Mg (CO3)4 and CdMg3(CO3)4, are predicted. No new phases are predicted in the CaCO3–MgCO3 system, but a low-lyi......
Mössbauer investigation of niningerite solid solutions (Mg,Fe)S
Physics and Chemistry of Minerals - Tập 10 - Trang 245-249 - 1984
57Fe Mössbauer spectra of (Mg,Fe)S solid solutions (niningerite) quenched from 1,000° C exhibit a singlet only within the composition range 8.4 to 50.0 mol. percent FeS. The isomer shift decreases progressively with increasing FeS content (from 0.99 to 0.95 mm/s) and extrapolates to a value of about 0.9 mm/s for FeS (halite structure), in close agreement with the isomer shift for FeS (troilite). ......
Melilite-type and melilite-related compounds: structural variations along the join Sr2−x Ba x MgSi2O7 (0 ≤ x ≤ 2) and high-pressure behavior of the two end-members
Physics and Chemistry of Minerals - Tập 39 - Trang 199-211 - 2011
The structural variations along the solid solution Sr2−x
Ba
x
MgSi2O7 (0 ≤ x ≤ 2), combined to the high-pressure characterization of the two end-members, have been studied. A topological change from the tetragonal (melilite-type) to the monoclinic (melilite-related) structure along the join Sr2MgSi2O7 (e.g.,
......
Low-temperature evolution of OH bands in synthetic forsterite, implication for the nature of H defects at high pressure
Physics and Chemistry of Minerals - Tập 40 - Trang 499-510 - 2013
We performed in situ infrared spectroscopic measurements of OH bands in a forsterite single crystal between −194 and 200 °C. The crystal was synthesized at 2 GPa from a cooling experiment performed between 1,400 and 1,275 °C at a rate of 1 °C per hour under high silica-activity conditions. Twenty-four individual bands were identified at low temperature. Three different groups can be distinguished:......
Static compression of α-Fe2O3: linear incompressibility of lattice parameters and high-pressure transformations
Physics and Chemistry of Minerals - Tập 30 - Trang 582-588 - 2003
The high-pressure behavior of α-Fe2O3 has been studied under static compression up to 60 GPa, using a laser-heated diamond anvil cell. Synchrotron-based angular-dispersive X-ray diffraction shows that the sample remains in the corundum structure up to 50 GPa, but with the appearance of coexisting diffraction lines from a high-pressure phase at pressures above 45 GPa. A least-squares fit of low-pre......
A vibrational study of phase transitions among the GeO2 polymorphs
Physics and Chemistry of Minerals - Tập 18 - Trang 7-18 - 1991
Infrared and Raman spectra of the quartz, rutile and amorphous forms of GeO2 have been recorded under pressure and/or temperature, in order to study the crystalline to crystalline — or amorphous — transformations of this compound in the solid state. X-ray diffraction data shown that crystalline quartz-GeO2 subjected to high pressure amorphizes. Infrared data are consistent with a gradual amorphisa......
Heat transfer in quartz, orthoclase, and sanidine at elevated temperature
Physics and Chemistry of Minerals - Tập 29 Số 9 - Trang 571-584 - 2002
The thermal diffusivity of quartz, orthoclase, and sanidine was measured in different directions by a transient method, to determine the second-rank tensor of thermal transport properties as a function of temperature up to 800 °C. Thermal diffusivity of phonons is described as D=1/3 v l, where v is the phonon velocity and l the mean free path length of phonons. In quartz the thermal diffusivity a......
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