The phase diagram of cobalt at high pressure and temperature: the stability of -cobalt and new -cobalt

This study experimentally investigates the Kalsilite-Nepheline-Diopside-Silica system at high pressure and temperature, with emphasis on silica-undersaturated volume (leucite-nepheline-diopside — Lct-Nph-Di; and kalsilite-nepheline-diopside — Kls + Nph + Di — planes), at 4.0 GPa (~120 km deep), temperatures up to 1,400ºC and dry conditions, to better understand the influence of K2O, Na2O, and CaO in alkali-rich silica-undersaturated magma genesis. In the Lct-Nph-Di plane, we determined the stability fields for kalsilite (Klsss), nepheline (Nphss) and clinopyroxene (Cpxss) solid solutions, wollastonite (Wo) and sanidine (Sa); and three piercing points: (i) pseudo-eutectic Kls + Nph + Di + liquid (Lct62Nph29Di9) at 1,000ºC; (ii) Kls + Sa + (Di + Wo) + liquid (Lct75Nph22Di2) at 1,200ºC; and (iii) pseudo-eutectic Kls + Di + Wo + liquid (Lct74Nph17Di9) at 1,000ºC. Kalsilite stability field represents a thermal barrier between ultrapotassic/potassic vs. sodic compositions. In the plane Kls-Nph-Di, we determined the stability fields for Klsss, Nphss and Cpxss and two aluminous phases in smaller proportions: spinel (Spl) and corundum (Crn). This plane has a piercing point in Kls + Nph + Di(± Spl) + liquid (Kls47Nph43Di10) at 1,100ºC. Our data showed that pressure extends K dissolution in Nph (up to 39 mol%) and Na in Kls (up to 27 mol%), and that these solid solutions, if present, determinate how much enriched in K and Na an alkaline magma will be in an alkaline-enriched metasomatic mantle. Additionally, we noted positive correlation between K2O and SiO2 concentration in experimental melts, negative correlation between CaO and SiO2, and no evident correlation between Na2O and SiO2.

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High-pressure, synthetic loveringite-davidite and its rare earth element geochemistry

Mineralogical Magazine ◽

10.1180/minmag.1987.051.359.16 ◽

1987 ◽

Vol 51 (359) ◽

pp. 145-149 ◽

Cited By ~ 4

Author(s):

T. H. Green ◽

N. J. Pearson

Keyword(s):

High Pressure ◽

Rare Earth ◽

Rare Earth Element ◽

Basaltic Andesite ◽

Upper Mantle ◽

Partition Coefficients ◽

Earth Element ◽

Element Geochemistry ◽

High Pressure And Temperature ◽

The Stability

AbstractLoveringite-davidite members of the crichtonite group were synthesized at high pressure and temperature (7.5 kbar, 1000–1050 °C) from a melt of TiO2 and rare earth element (REE) enriched basaltic andesite composition. Four sets of partition coefficients for La, Srn, Ho, Lu and Sr (analogue for Eu2+) were obtained. These show that light and heavy REE are readily accommodated, but the intermediate REE are discriminated against in the loveringite—davidite structure. This confirms the previously proposed two sites (A and M) for REE substitution in the crichtonite group. Additional experiments verified the stability of REE-rich crichtonite group minerals to 20 kbar, 1300 °C and 30 kbar, 1000 °C, and indicate that this phase may be an important accessory repository for the light and heavy REE in the upper mantle.

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New insights on the GeSe x Te1−x phase diagram from theory and experiment

Acta Crystallographica Section B Structural Science Crystal Engineering and Materials ◽

10.1107/s2052520619001847 ◽

2019 ◽

Vol 75 (2) ◽

pp. 246-256 ◽

Cited By ~ 2

Author(s):

Markus Guido Herrmann ◽

Ralf Peter Stoffel ◽

Michael Küpers ◽

Mohammed Ait Haddouch ◽

Andreas Eich ◽

...

Keyword(s):

Phase Diagram ◽

High Pressure ◽

Low Temperature ◽

Hexagonal Phase ◽

Structure Type ◽

Stability Field ◽

Temperature Behaviour ◽

Formation Enthalpies ◽

The Stability

The high-pressure and low-temperature behaviour of the GeSe x Te1−x system (x = 0, 0.2, 0.5, 0.75, 1) was studied using a combination of powder diffraction measurements and first-principles calculations. Compounds in the stability field of the GeTe structure type (x = 0, 0.2, 0.5) follow the high-pressure transition pathway: GeTe-I (R3m) → GeTe-II (f.c.c.) → GeTe-III (Pnma). The newly determined GeTe-III structure is isostructural to β-GeSe, a high-pressure and high-temperature polymorph of GeSe. Pressure-dependent formation enthalpies and stability regimes of the GeSe x Te1−x polymorphs were studied by DFT calculations. Hexagonal Ge4Se3Te is stable up to at least 25 GPa. Significant differences in the high-pressure and low-temperature behaviour of the GeTe-type structures and the hexagonal phase are highlighted. The role of Ge...Ge interactions is elucidated using the crystal orbital Hamilton population method. Finally, a sketch of the high-pressure phase diagram of the system is provided.

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The stability and Raman spectra of ikaite, CaCO3{middle dot}6H2O, at high pressure and temperature

American Mineralogist ◽

10.2138/am.2005.1783 ◽

2005 ◽

Vol 90 (11-12) ◽

pp. 1835-1839 ◽

Cited By ~ 18

Author(s):

A. Shahar

Keyword(s):

High Pressure ◽

Raman Spectra ◽

High Pressure And Temperature ◽

The Stability

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High pressure measurements of the He-Ne binary phase diagram at 296 K: Evidence for the stability of a stoichiometric Ne(He)2solid

Physical Review Letters ◽

10.1103/physrevlett.70.178 ◽

1993 ◽

Vol 70 (2) ◽

pp. 178-181 ◽

Cited By ~ 58

Author(s):

Paul Loubeyre ◽

Michel Jean-Louis ◽

René LeToullec ◽

Lydie Charon-Gérard

Keyword(s):

Phase Diagram ◽

High Pressure ◽

Binary Phase Diagram ◽

Pressure Measurements ◽

Binary Phase ◽

The Stability

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Unexpected coordination number and phase diagram of niobium diselenide under compression

Physical Chemistry Chemical Physics ◽

10.1039/c7cp00805h ◽

2017 ◽

Vol 19 (20) ◽

pp. 13219-13229 ◽

Cited By ~ 4

Author(s):

Zhong-Li Liu ◽

Hong Jia ◽

Rui Li ◽

Xiu-Lu Zhang ◽

Ling-Cang Cai

Keyword(s):

Phase Diagram ◽

High Pressure ◽

Coordination Number ◽

Harmonic Approximation ◽

Temperature Phase ◽

High Pressure And Temperature ◽

Niobium Diselenide ◽

Temperature Phase Diagram

We discovered several new high-pressure structures of NbSe2 with unexpected coordination number and constructed its high pressure and temperature phase diagram based on quasi-harmonic approximation.

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Phase transition and thermodynamic properties of beryllium telluride under high pressure

International Journal of Modern Physics B ◽

10.1142/s0217979215500964 ◽

2015 ◽

Vol 29 (15) ◽

pp. 1550096

Author(s):

Zhi-Cheng Guo ◽

Fen Luo ◽

Xiu-Lu Zhang ◽

Cheng-An Liu ◽

Ling-Cang Cai

Keyword(s):

Phase Diagram ◽

High Pressure ◽

Thermodynamic Properties ◽

Density Functional ◽

Phonon Dispersion ◽

Structural Parameters ◽

Theoretical Work ◽

Debye Model ◽

Dielectric Tensor ◽

High Pressure And Temperature

A theoretical investigation on structural, dynamical, phase diagram and thermodynamic properties of beryllium telluride (BeTe) under high pressure and temperature is presented in the framework of density functional theory. The calculated structural parameters of BeTe in both zinc blende (ZB) and nickel arsenide (NiAs) structures are in reasonable agreement with available experimental data and previous theoretical work. The phonon dispersion relations, dielectric tensor and Born effective charge are investigated within the density functional perturbation theory (DFPT). The investigation of the phase diagram indicated that the NiAs structure BeTe becomes stable at high pressure and temperature. Based on the quasiharmonic Debye model, the pressure and temperature dependences of bulk modulus, Grüneisen parameter, Debye temperature, specific heat and thermal expansion coefficient are all successfully obtained. We hope that the theoretical results reported here can give more insight into the structural and thermodynamic properties of other semiconductors at high temperature and pressure.

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