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High-pressure form of pyrite-type germanium dioxide ...

The new high-pressure IrO2 phase has a pyrite-type structure with space group Pa-3 and cubic symmetry. The phase was stable at pressures up to 50 GPa. The pyrite-type IrO2 structure is …

Polyamorphism of GeO2 Glass at High Pressure - Hong ...

Three pressure‐induced polyamorphs in GeO 2 glass are recognized unambiguously at high pressure, i.e., α‐quartz‐like, rutile‐like, and pyrite‐like amorphous structures. The obtained knowledge of these polyamorphs is helpful for understanding the mechanisms of network compression behavior and physical properties of SiO 2 and GeO 2 ...

HPSTAR -

Through high-pressure-temperature experiments in a laser-heated diamond anvil cell at 107–136 GPa and 2,400 K, we discovered an ultradense hydrous phase in (Fe0.8Al0.2)OOH with a previously unknown hexagonal lattice. The team includes Li Zhang, Hongsheng Yuan, Ho-kwang Mao of HPSTAR, and Yue Meng of High Pressure Collaborative Access Team ...

Phase transitions in ε-FeOOH at high pressure and ambient ...

Recently, a great deal of attention has been paid to the high-pressure polymorphs of FeOOH (space groups P2 1 nm and Pnnm). These structures potentially form a hydrogen-bearing solid solution with AlOOH and phase H (MgSiO 4 H 2) that may transport water (OH –) deep into the Earth's lower mantle. Additionally, the pyrite-type polymorph (space ...

A theoretical study of band-gap and electrical resistivity ...

The pressure dependence of electrical resistivity of FeS 2 (pyrite) has been studied with the help of a simple analytical relation. The calculated results are found in reasonable agreement with the experimental measurements. The computed results are then utilized for the evaluation of pressure dependence of band-gap of FeS 2 (pyrite). The ...

Structural stability of silica at high pressures and ...

The high-pressure phase diagram of $mat{Si}{mat{O}}_{2}$ has been calculated using density-functional perturbation theory. We find that phase transitions of silica do not correspond to any observed seismic discontinuities within the Earth. We analyze the breakdown of close packing occurring in $mat{Si}{mat{O}}_{2}$ above …

mp-226: FeS2 (cubic, Pa-3, 205) - Materials Project

FeS2 is Pyrite structured and crystallizes in the cubic Pa-3 space group. The structure is three-dimensional. Fe3+ is bonded to six equivalent S+1.50- atoms to form corner-sharing FeS6 octahedra. The corner-sharing octahedral tilt angles are 64°. All Fe–S bond lengths are 2.25 Å. S+1.50- is bonded in a 3-coordinate geometry to three equivalent Fe3+ atoms.

The band gap and electrical resistivity of FeS2-pyrite at ...

The indirect energy gap and electrical resistivity of FeS 2-pyrite have been measured at high pressures and 300 K using optical absorption spectroscopy and electrical conductivity measurements. Absorption spectra extend to ∼28 GPa, while resistivity is determined to ∼34 GPa.The band gap of FeS 2 is indirect throughout this pressure range and decreases linearly with pressure at …

The pyrite-type high-pressure form of FeOOH

The pyrite-type high-pressure form of FeOOH Nature. 2017 Jul 13;547(7662):205-208. doi: 10.1038/nature22823. Epub 2017 Jul 3. Authors Masayuki Nishi 1 2, Yasuhiro Kuwayama 1 3, Jun Tsuchiya 1 2, Taku Tsuchiya 1 2 Affiliations 1 Geodynamics Research Center, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime 790 ...

Ultrahigh‐Pressure Phase Transitions in FeS2 and FeO2 ...

Recent studies have successfully synthesized pyrite-type ( ) FeO 2 (Figure S1a in the supporting information) by chemical combination of Fe 2 O 3 and O 2 or dissociation of FeOOH under high pressure and high temperature, which could not only provide an alternative interpretation for origin of seismic anomalies in Earth's lower mantle but also ...

(PDF) Equation of state, elasticity, and shear strength of ...

The transport activation energy of natural pyrite is ~0.045 eV at ambient pressure, which corresponds to the activation of the CoFe donor level (~1/2 ED), and decreases with increasing pressure ...

Single-crystal structure of pyrite-type HP-Pd₀.₈₄₍₁₎Se₂ ...

If pressure is applied, the coordination number of palladium atoms increases and the three-dimensional pyrite-type structure with octahedral (PdSe₆)⁴⁻ coordination geometry is observed. For the first time, single crystals of a pyrite-type PdSe₂ modification could be obtained and characterized, which were grown by multianvil high ...

Pyrite form of group-14 element pernitrides synthesized at ...

Pyrite form of group-14 element pernitrides synthesized at high pressure and high temperature K. Niwa, H. Ogasawara and M. Hasegawa, Dalton Trans., 2017, 46, 9750 DOI: 10.1039/C7DT01583F

New High-pressure form of Pyrite-type Silica under ...

New High-pressure form of Pyrite-type Silica under Multimegabar Pressure Fig. 1. Phase diagram of SiO2. Open circles and solid squares indicate the stabilities of α-PbO2-type and pyrite-type phases, respectively. 1000 1500 2000 2500 Pyrite-type CaC l 2 Rutile-type vite) -type 0 100 200 300 360 Te mperature (K) 50 150 250 Pressure (GPa) 1000 ...

High-pressure induced phase transition of FeS 2 ...

Abstract Being as the most abundant natural mineral among the iron-based sulphides, iron pyrite (FeS2) has been extensively investigated. These investigations mainly focused on the known marcasite (Pnnm) and pyrite ( P a 3 ¯ ) phases, due to unknown of high pressure (HP) structural phases of FeS2. Here, we report a theoretical study up to 300 GPa to uncover a brand new monoclinic HP phase of ...

Phys. Rev. B 99, 045153 (2019) - Ultrahigh-pressure form ...

High-pressure synthesis of denser glass has been a longstanding interest in condensed-matter physics and materials science because of its potentially broad industrial application. Nevertheless, understanding its nature under extreme pressures has yet to be clarified due to experimental and theoretical challenges. Here we reveal the formation of $mat{OS}{mat{i}}_{4}$ tetraclusters ...

[PDF] High pressure compressibilities of pyrite and ...

Compressibilities of pyrite and cattierite have been examined by the single-crystal X-ray diffraction method up to 42 kbar and 36 kbar, respectively. Both S-S and M-S (M: Fe, Co) bonds in both of the minerals are contracted linearly with pressure within the experimental pressure ranges. However, contraction of the S-S bond in cattierite is much smaller than that in pyrite, whereas the CooSbond ...

A tetragonal high-pressure phase of PtAs 2 - NASA/ADS

A tetragonal high-pressure phase of PtAs 2 with I4/mmm symmetry was first discovered above 90 GPa by using first principle swarm intelligence structure search technique. The first order structure transition character of PtAs 2 from the ambient-pressure cubic pyrite phase to this tetragonal HP phase was confirmed by a large volume reduction of 8.1%.

The pyrite-type high-pressure form of silica

Silica (SiO2) exhibits extensive polymorphism at elevated pressures. X-ray diffraction measurements showed that a high-pressure form with a pyrite-type structure, denser than other known silica phases, is stable above 268 giga-pascals and 1800 kelvin. The silicon coordination number increases from 6 …

The pyrite-type high-pressure form of FeOOH

The pyrite-type high-pressure form of FeOOH Hydrogen (H) is the most abundant element in the universe and it has played an important role in the structure, dynamics, and evolution of the Earth. About 70% of the Earth's surface is covered with water (H 2O) and a huge amount of water is also estimated to be maintained in the Earth's interior.

The pyrite-type high-pressure form of FeOOH | Nature

The pyrite-type high-pressure form of FeOOH is predicted from first principles, and found experimentally to be stable under the conditions at the base of the mantle, with implications for ...

Structural phase transition and mechanical properties of ...

A systematic examination of structural phase transitions and mechanical properties for TiO 2 under high pressure has been performed by using first‐principles calculations. First, we show that the orthorhombic Pca21 structure becomes stabilize at certain pressure and temperature, whereas the cubic fluorite and pyrite structures are not energetically viable in the whole pressure range of 0 ...

Surface passivation model explains pyrite oxidation ...

As the carbonate buffer system was weaker in the high pressure experiments due to the tenfold dilution of the inflowing water, the effect of pyrite oxidation resulted in a minor influence on the pH (values of 6.2–7.5), even as the pyrite oxidation rates were smaller in the high pressure experiment compared to the low pressure experiments.

Isotopic Compositions of Sulfides in Exhumed High‐Pressure ...

Thus, pyrite breakdown to pyrrhotite reactions operating during subduction metamorphism should produce oxidized Fe-depleted peak mineral assemblages in exhumed high-pressure rocks. Additionally, the low solubility of reduced sulfur species in rock-buffered systems suggests that sulfides may continue to persist in the slab (Evans et al., 2014 ...

Stable magnesium peroxide at high pressure | Scientific ...

For example, magnesium peroxide (MgO 2) have been synthesized at near-ambient conditions and at high oxygen fugacities in the pyrite-type ( Pa3) structure 11. However, Pa3 MgO 2 is ...

PYRITE ROASTING, AN ALTERNATIVE TO SULPHUR BURNING …

system for the production of high-pressure steam. Pyrite grain size is usually s up to 6mm in diameter. The coarser the grain, the higher the gas velocity must be to maintain the bed in a fluidized state. Even flotation pyrites with a grain size less than 70 µm can be processed in the fluid bed roaster. Gas velocity

Iron oxide - Wikipedia

goethite (α-FeOOH),; akaganéite (β-FeOOH),; lepidocrocite (γ-FeOOH),; feroxyhyte (δ-FeOOH),; ferrihydrite (approx.), or, better recast as ; high-pressure pyrite-structured FeOOH. Once dehydration is triggered, this phase may form (< <).; schwertmannite (ideally () or + (,)); green rust (() + where A − is Cl − or 0.5SO 4 2−); Microbial degradation. Several species of bacteria ...

In Situ Electrochemical Investigation of Acidic Pressure ...

pressure oxidation process, gold bearing pyrite is subjected to high-temperature, high-pressure oxidation in autoclaves to destroy pyrite lattice.12,13 This process has been practiced commercially since the early1980s,14 and is widely accepted by the gold mining industry all over the world for its high efficiency and low pollution.

Sulfur isotope compositions of pyrite from high-pressure ...

Previous research (Li et al., 2013, Li et al., 2016) and this study show that the studied high-pressure rocks and their veins are dominated by pyrite while minor chalcopyrite, and rare pyrrhotite, bornite, chalcocite, sphalerite, galena, arsenopyrite, cobalt-pentlandite and enargite contribute to a minor extent to the sulfur budget of the bulk ...

The Pyrite-Type High-Pressure Form of Silica

The Pyrite-Type High-Pressure Form of Silica Yasuhiro Kuwayama,1* Kei Hirose,1,2 Nagayoshi Sata,2 Yasuo Ohishi3 Silica (SiO 2) exhibits extensive polymorphism at elevated pressures. X-ray dif-fraction measurements showed that a high-pressure form with a pyrite-type structure, denser than other known silica phases, is stable above 268 giga-

High-pressure Cu–Fe–S Phase Equilibria: some Experimental ...

The effect of pressure on Fe–S phase equilibria. High-pressure phase relations in the Fe–S system have been explored to high T and P, and the pyrite–pyrrhotite relation persists to P and T conditions well beyond those found along the Earth`s subduction geotherms.

Pyrite Mineral | Uses and Properties

What is Pyrite? Pyrite is a brass-yellow mineral with a bright metallic luster.It has a chemical composition of iron sulfide (FeS 2) and is the most common sulfide mineral.It forms at high and low temperatures and occurs, usually in small quantities, in igneous, metamorphic, and sedimentary rocks worldwide. Pyrite is so common that many geologists would consider it to be a ubiquitous mineral.