Studying the Stability of the K/Ar Isotopic System of Phlogopites in Conditions of High T, P: 40Ar/39Ar Dating, Laboratory Experiment, Numerical Simulation

Typically, 40Ar/39Ar dating of phlogopites from deep-seated xenoliths of kimberlite pipes produces estimates that suggest much older ages than those when these pipes were intruded. High-pressure (3 GPa) laboratory experiments enabled the authors to explore the behaviour of argon in the phlogopite structure under the conditions that correspond to the mantle, at the temperatures (from 700 to 1000 °С), far exceeding closure temperature of the K/Ar isotopic system. “Volume diffusion” remains foremost for describing the mobility of argon in phlogopite at high pressures. The mantle material age can be estimated through the dating of the phlogopites from deep-seated xenoliths of kimberlites, employing the 40Ar/39Ar method, subject to correction for a partial loss of radiogenic 40Ar when xenolith moves upwards to the Earth’s surface. The obtained data served as the basis for proposing the behaviour model of the K/Ar isotopic system of minerals in conditions of great depths (lower crust, mantle), and when transporting xenoliths in the kimberlite melt.

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Crystal structures and dynamical properties of dense CO2

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1601254113 ◽

2016 ◽

Vol 113 (40) ◽

pp. 11110-11115 ◽

Cited By ~ 21

Author(s):

Xue Yong ◽

Hanyu Liu ◽

Min Wu ◽

Yansun Yao ◽

John S. Tse ◽

...

Keyword(s):

High Pressure ◽

High Pressures ◽

Theoretical Calculations ◽

Ambient Pressure ◽

Md Simulations ◽

Ab Initio Molecular Dynamics ◽

Structural Polymorphism ◽

Stability Structure ◽

Dynamical Properties ◽

The Stability

Structural polymorphism in dense carbon dioxide (CO2) has attracted significant attention in high-pressure physics and chemistry for the past two decades. Here, we have performed high-pressure experiments and first-principles theoretical calculations to investigate the stability, structure, and dynamical properties of dense CO2. We found evidence that CO2-V with the 4-coordinated extended structure can be quenched to ambient pressure below 200 K—the melting temperature of CO2-I. CO2-V is a fully coordinated structure formed from a molecular solid at high pressure and recovered at ambient pressure. Apart from confirming the metastability of CO2-V (I-42d) at ambient pressure at low temperature, results of ab initio molecular dynamics and metadynamics (MD) simulations provided insights into the transformation processes and structural relationship from the molecular to the extended phases. In addition, the simulation also predicted a phase V′(Pna21) in the stability region of CO2-V with a diffraction pattern similar to that previously assigned to the CO2-V (P212121) structure. Both CO2-V and -V′ are predicted to be recoverable and hard with a Vicker hardness of ∼20 GPa. Significantly, MD simulations found that the CO2 in phase IV exhibits large-amplitude bending motions at finite temperatures and high pressures. This finding helps to explain the discrepancy between earlier predicted static structures and experiments. MD simulations clearly indicate temperature effects are critical to understanding the high-pressure behaviors of dense CO2 structures—highlighting the significance of chemical kinetics associated with the transformations.

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Phase transitions of BaCO3 at high pressures

Mineralogical Magazine ◽

10.1180/minmag.2008.072.2.659 ◽

2008 ◽

Vol 72 (2) ◽

pp. 659-665 ◽

Cited By ~ 10

Author(s):

S. Ono ◽

J. P. Brodholt ◽

G. D. Price

Keyword(s):

Phase Transition ◽

Experimental Study ◽

High Pressure ◽

Phase Transitions ◽

Bulk Modulus ◽

First Principles ◽

High Pressures ◽

Ambient Conditions ◽

The Stability ◽

Previous Experimental Study

AbstractFirst-principles simulations and high-pressure experiments were used to study the stability of BaCO3 carbonates at high pressures. Witherite, which is orthorhombic and isotypic with CaCO3 aragonite, is stable at ambient conditions. As pressure increases, BaCO3 transforms from witherite to an orthorhombic post-aragonite structure at 8 GPa. The calculated bulk modulus of the post-aragonite structure is 60.7 GPa, which is slightly less than that from experiments. This structure shows an axial anisotropicc ompressibility and the a axis intersects with the c axis at 70 GPa, which implies that the pressure-induced phase transition reported in previous experimental study is misidentified. Although a pyroxene-like structure is stable in Mg- and Ca-carbonates at pressures >100 GPa, our simulations showed that this structure does not appear in BaCO3.

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Electronic Properties of Magnetic Superconductor HoNi2B2C Under High Pressure

International Journal of Modern Physics B ◽

10.1142/s0217979203021587 ◽

2003 ◽

Vol 17 (18n20) ◽

pp. 3664-3671 ◽

Cited By ~ 6

Author(s):

G. Oomi ◽

N. Matsuda ◽

T. Kagayama ◽

C. K. Cho ◽

P. C. Canfield

Keyword(s):

Magnetic Field ◽

High Pressure ◽

Electrical Resistivity ◽

Fermi Liquid ◽

High Pressures ◽

Metamagnetic Transition ◽

Liquid Behavior ◽

The Stability ◽

Normal Fermi ◽

Fermi Liquid Behavior

The electrical resistivity of single crystalline HoNi 2 B 2 C has been measured at high pressure and magnetic fields. The three anomalies in the magnetoresistance due to metamagnetic transitions are observed both at ambient and high pressures. It is found that the metamagnetic transition fields increase with increasing pressure. The temperature dependence of electrical resistivity is strongly dependent on magnetic field. Non Fermi liquid behavior is observed near the metamagnetic transition fields. But the normal Fermi liquid behavior recovers after completing the phase transition. The Grüneisen parameters are also calculated to examine the stability of electronic state.

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The Effect of Pulsed Laser Heating on the Stability of Ferropericlase at High Pressures

Minerals ◽

10.3390/min10060542 ◽

2020 ◽

Vol 10 (6) ◽

pp. 542

Author(s):

Georgios Aprilis ◽

Anna Pakhomova ◽

Stella Chariton ◽

Saiana Khandarkhaeva ◽

Caterina Melai ◽

...

Keyword(s):

High Pressure ◽

Lower Mantle ◽

Laser Heating ◽

High Pressures ◽

Pulsed Laser ◽

Experimental Conditions ◽

Lowermost Part ◽

The Stability ◽

Pulsed Laser Heating ◽

Calcium Silicate Perovskite

It is widely accepted that the lower mantle consists of mainly three major minerals—ferropericlase, bridgmanite and calcium silicate perovskite. Ferropericlase ((Mg,Fe)O) is the second most abundant of the three, comprising approximately 16–20 wt% of the lower mantle. The stability of ferropericlase at conditions of the lowermost mantle has been highly investigated, with controversial results. Amongst other reasons, the experimental conditions during laser heating (such as duration and achieved temperature) have been suggested as a possible explanation for the discrepancy. In this study, we investigate the effect of pulsed laser heating on the stability of ferropericlase, with a geochemically relevant composition of Mg0.76Fe0.24O (Fp24) at pressure conditions corresponding to the upper part of the lower mantle and at a wide temperature range. We report on the decomposition of Fp24 with the formation of a high-pressure (Mg,Fe)3O4 phase with CaTi2O4-type structure, as well as the dissociation of Fp24 into Fe-rich and Mg-rich phases induced by pulsed laser heating. Our results provide further arguments that the chemical composition of the lower mantle is more complex than initially thought, and that the compositional inhomogeneity is not only a characteristic of the lowermost part, but includes depths as shallow as below the transition zone.

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Unconventional Stoichiometries of Na–O Compounds at High Pressures

Materials ◽

10.3390/ma14247650 ◽

2021 ◽

Vol 14 (24) ◽

pp. 7650

Author(s):

Lihua Yang ◽

Yukai Zhang ◽

Yanli Chen ◽

Xin Zhong ◽

Dandan Wang ◽

...

Keyword(s):

High Pressure ◽

High Pressures ◽

Stability Field ◽

First Principles Calculations ◽

One Dimensional ◽

Theoretical Investigations ◽

Systematic Structure ◽

Pressure Stability ◽

The Stability ◽

New Compounds

It has been realized that the stoichiometries of compounds may change under high pressure, which is crucial in the discovery of novel materials. This work uses systematic structure exploration and first-principles calculations to consider the stability of different stoichiometries of Na–O compounds with respect to pressure and, thus, construct a high-pressure stability field and convex hull diagram. Four previously unknown stoichiometries (NaO5, NaO4, Na4O, and Na3O) are predicted to be thermodynamically stable. Four new phases (P2/m and Cmc21 NaO2 and Immm and C2/m NaO3) of known stoichiometries are also found. The O-rich stoichiometries show the remarkable features of all the O atoms existing as quasimolecular O2 units and being metallic. Calculations of the O–O bond lengths and Bader charges are used to explore the electronic properties and chemical bonding of the O-rich compounds. The Na-rich compounds stabilized at extreme pressures (P > 200 GPa) are electrides with strong interstitial electron localization. The C2/c phase of Na3O is found to be a zero-dimensional electride with an insulating character. The Cmca phase of Na4O is a one-dimensional metallic electride. These findings of new compounds with unusual chemistry might stimulate future experimental and theoretical investigations.

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Microfluidic active pressure and flow stabiliser

Scientific Reports ◽

10.1038/s41598-021-01865-4 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Simon Södergren ◽

Karolina Svensson ◽

Klas Hjort

Keyword(s):

High Pressure ◽

High Pressures ◽

Thermal Control ◽

Dead Volume ◽

Glass Chip ◽

Total Analysis ◽

The Stability ◽

Upstream Flow

AbstractIn microfluidics, a well-known challenge is to obtain reproducible results, often constrained by unstable pressures or flow rates. Today, there are existing stabilisers made for low-pressure microfluidics or high-pressure macrofluidics, often consisting of passive membranes, which cannot stabilise long-term fluctuations. In this work, a novel stabilisation method that is able to handle high pressures in microfluidics is presented. It is based on upstream flow capacitance and thermal control of the fluid’s viscosity through a PID controlled restrictor-chip. The stabiliser consists of a high-pressure-resistant microfluidic glass chip with integrated thin films, used for resistive heating. Thereby, the stabiliser has no moving parts. The quality of the stabilisation was evaluated with an ISCO pump, an HPLC pump, and a Harvard pump. The stability was greatly improved for all three pumps, with the ISCO reaching the highest relative precision of 0.035% and the best accuracy of 8.0 ppm. Poor accuracy of a pump was compensated for in the control algorithm, as it otherwise reduced the capacity to stabilise longer times. As the dead volume of the stabiliser was only 16 nL, it can be integrated into micro-total-analysis- or other lab-on-a-chip-systems. By this work, a new approach to improve the control of microfluidic systems has been achieved.

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Analysis of the ‘Friction Factor Jump’ Phenomenon in Hole-Pattern Seals

Volume 1B, Symposia: Fluid Machinery; Fluid Power; Fluid-Structure Interaction and Flow-Induced Noise in Industrial Applications; Flow Applications in Aerospace; Flow Manipulation and Active Control: Theory, Experiments and Implementation; Fundamental Issues and Perspectives in Fluid Mechanics ◽

10.1115/fedsm2013-16122 ◽

2013 ◽

Author(s):

Aarthi Sekaran ◽

Gerald Morrison

Keyword(s):

Experimental Investigation ◽

High Pressure ◽

Shear Layer ◽

Friction Factor ◽

Pressure Fluctuation ◽

High Pressures ◽

Sudden Change ◽

Flow Models ◽

The Difference ◽

The Stability

Hole-pattern and honeycomb seals are used to replace labyrinth seals in turbomachinery that are experiencing vibration problems, such as high pressure gas compressors. Computer simulations used to investigate the stability of a rotordynamic system require information about the stiffness, damping, and added mass generated by bearings and seals. These codes typically use bulk flow models for the fluid flow inside the bearings and seals which require empirical information about how the friction factor and leakage rate vary with rotor speed and pressure drop across the seal. Historically, experimental facilities were constructed to provide empirical data which were then used in the rotordynamic models. Ha et al (1992) observed a sudden change in the flow rate and resulting friction factor in a honeycomb seal as the pressure differential across the seal increased. This ‘friction factor jump’ was attributed to the shear flow over a seal cavity changing from a dominant normal mode to a dominant feedback mode. This was confirmed through pressure spectra showing that indeed, the shear layer instability mode changed and the frequencies present compared to predicted values. A similar effect has recently been observed in hole-pattern seals operating at high pressures, 84 bar (1200 psi). However, the pressure fluctuation spectra did not confirm the same mode change observed by Ha. The friction factor changed a by factor of around three in this instance which can drastically change the stability of the rotating system. This high pressure flow has a higher Reynolds number due to the high pressures which may explain the difference. An experimental investigation has confirmed the presence of the “friction factor jump” and that there is a change in the pressure fluctuation spectra. Further experimental investigation coupled with Large Eddy Simulation (LES) of the flow field have confirmed there is a change in the shear layer over the cavity but not the same as observed by Ha. Comparisons between the experimental and computational results are made along with an explanation of the flow phenomena.

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