Advances in Computation of Temperature-Pressure Phase Diagrams of High-Pressure Nitrides

2008 ◽  
Vol 403 ◽  
pp. 77-80 ◽  
Author(s):  
Peter Kroll

A combination of first-principle and thermochemical calculations is applied to compute the phase diagrams of rhenium-nitrogen and of ruthenium-nitrogen at elevated temperature and high pressure. We augment total energy calculations with our approach to treat the nitrogen fugacity at high pressures. We predict a sequential nitridation of Re at high-pressure/high-temperature conditions. At 3000 K, ReN will form from Re and nitrogen at about 32 GPa. A ReN2 with CoSb2-type structure may be achieved at pressures exceeding 50 GPa at this temperature. Marcasite-type RuN2 will be attainable at 3000 K at pressures above 30 GPa by reacting Ru with nitrogen.

2007 ◽  
Vol 1040 ◽  
Author(s):  
Peter Kroll

AbstractWe apply our procedure of including nitrogen fugacity into thermochemical calculations to compute phase diagrams in the rhenium-nitrogen and ruthenium-nitrogen systems. The combination of first-principle and thermochemical calculations let us predict the sequential nitridation of Re at high-pressure/high-temperature conditions. At 3000 K, Re will react with nitrogen at about 32 GPa yielding ReN. Formation of ReN2 with CoSb2-type structure is predicted for pressures exceeding 50 GPa at this temperature. The recently proposed marcasite-type RuN2 will be attainable at 3000 K at pressures above 30 GPa from a mixture of Ru and RuN2.


2006 ◽  
Vol 987 ◽  
Author(s):  
Peter Kroll

AbstractWe propose an explicit scheme to include the fugacity of nitrogen in computations of phase diagrams of nitride compounds at high-temperature/high-pressure conditions. The assessment is based on available thermochemical data and two kind of extrapolating functions to provide upper and lower boundary for the fugacity coefficient as a funtion of p and T. The procedure is applied to investigate the synthesis of novel nitrides of tantalum, tungsten, and platinum. The combination of first-principle and thermochemical calculations let us predict the synthesis of a new high-pressure phase of Ta3N5 at about 27 GPa. Synthesis of WN2 becomes feasible at about 45 GPa. We furthermore explain why the synthesis of the noble metal subnitride, PtN2, occurs at about 40 GPa, and why PtN is not accessible in high-pressure experiments.


2017 ◽  
Vol 19 (40) ◽  
pp. 27406-27412 ◽  
Author(s):  
Yanbin Ma ◽  
Defang Duan ◽  
Ziji Shao ◽  
Da Li ◽  
Liyuan Wang ◽  
...  

Invigorated by the high temperature superconductivity in some binary hydrogen-dominated compounds, we systematically explored high-pressure phase diagrams and superconductivity of a ternary Mg–Ge–H system usingab initiomethods.


2003 ◽  
Vol 58 (4) ◽  
pp. 257-265 ◽  
Author(s):  
Hubert Huppertz

A new oxoborate β -CaB4O7 has been synthesized under high-pressure/high-temperature conditions from calcium oxide and boron oxide with a Walker-type multianvil apparatus at 7.7 GPa and 1100 °C. Single crystal X-ray structure determination of β -CaB4O7 revealed: Pmn21, a = 1058.4(1), b = 436.9(1), c = 419.4(1) pm, Z = 2, R1 = 0.0305, wR2 = 0.0587 (all data). The compound is isotypic to the known oxoborates SrB4O7, PbB4O7, and EuB4O7 exhibiting a network structure of linked BO4 tetrahedra. As a prominent feature of the tetrahedral network an oxygen atom is coordinated to three boron atoms. The relation of the crystal structure of the high-pressure phase β -CaB4O7 to the normalpressure phase α-CaB4O7 as well as the relation to the isotypic phases MB4O7 (M = Sr, Pb, Eu) are discussed. The results of IR-spectroscopic investigations on β -CaB4O7 are also presented.


2006 ◽  
Vol 61 (12) ◽  
pp. 1561-1565 ◽  
Author(s):  
Natalia Dubrovinskaia ◽  
Leonid Dubrovinsky ◽  
Nobuyoshi Miyajima ◽  
Falko Langenhorst ◽  
Wilson A. Crichton ◽  
...  

Bulk samples (with volumes up to ~ 7.5 mm3) of boron-doped diamonds (BDD) were synthesized by means of direct reaction between boron carbide and graphite in a multianvil apparatus at high pressures and high temperatures (HPHT). X-ray diffraction data revealed the presence in BDD of a very small amount of a highly boron-enriched phase (B50C2) and traces of the B13C2 used as an initial material. The absence of B50C2 in the product of treatment of pure B13C2 under the same HPHT conditions suggests that boron-rich carbides exsolute from diamond on quenching leading to boron depletion of the diamond matrix. These observations imply that boron solubility in diamond increases at high pressure and high temperature. This result may have important implications for the understanding of the mechanism of boron incorporation into diamond at HPHT synthesis and for the interpretation of the data on superconductivity of polycrystalline BDD.


Crystals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 676 ◽  
Author(s):  
Raquel Chuliá-Jordán ◽  
David Santamaría-Pérez ◽  
Tomás Marqueño ◽  
Javier Ruiz-Fuertes ◽  
Dominik Daisenberger

The laser-heating diamond-anvil cell technique enables direct investigations of materials under high pressures and temperatures, usually confining the samples with high yield strength W and Re gaskets. This work presents experimental data that evidences the chemical reactivity between these refractory metals and CO2 or carbonates at temperatures above 1300 °Ϲ and pressures above 6 GPa. Metal oxides and diamond are identified as reaction products. Recommendations to minimize non-desired chemical reactions in high-pressure high-temperature experiments are given.


1981 ◽  
Vol 36 (11) ◽  
pp. 1169-1176 ◽  
Author(s):  
V. M. Valyashko ◽  
M. Buback ◽  
E. U. Franck

The infrared absorption of the O-D stretching fundamental of HDO in concentrated aqueous (HDO/H2O)NaClO4 solutions up to 20 mole% salt has been measured. The data for the wave-number of maximum absorption, ν̅(max), and for the integrated molar absorptivity B up to pressures and temperatures of 2800 bar and 250 °C, respectively, demonstrate the importance of non-hydrogen-bonded interactions in aqueous perchlorate solutions. A non-continuous dis­tribution of the states of water molecules is clearly evident from the experimental spectra. A band separation using three Gaussian components proves the close similarity between the high-pressure high-temperature vibrational O-D infrared spectra of aqueous perchlorate solutions and the O-D Raman spectra of water and aqueous solutions.Results of the band separation together with literature Raman data provide some evidence that a transition from “water-like” to “melt-like” behaviour occurs in a fairly narrow concentra­tion region between 10 and 15 mole% salt.


2021 ◽  
Vol 12 (1) ◽  
Author(s):  
K. Mukasa ◽  
K. Matsuura ◽  
M. Qiu ◽  
M. Saito ◽  
Y. Sugimura ◽  
...  

AbstractThe interplay among magnetism, electronic nematicity, and superconductivity is the key issue in strongly correlated materials including iron-based, cuprate, and heavy-fermion superconductors. Magnetic fluctuations have been widely discussed as a pairing mechanism of unconventional superconductivity, but recent theory predicts that quantum fluctuations of nematic order may also promote high-temperature superconductivity. This has been studied in FeSe1−xSx superconductors exhibiting nonmagnetic nematic and pressure-induced antiferromagnetic orders, but its abrupt suppression of superconductivity at the nematic end point leaves the nematic-fluctuation driven superconductivity unconfirmed. Here we report on systematic studies of high-pressure phase diagrams up to 8 GPa in high-quality single crystals of FeSe1−xTex. When Te composition x(Te) becomes larger than 0.1, the high-pressure magnetic order disappears, whereas the pressure-induced superconducting dome near the nematic end point is continuously found up to x(Te) ≈ 0.5. In contrast to FeSe1−xSx, enhanced superconductivity in FeSe1−xTex does not correlate with magnetism but with the suppression of nematicity, highlighting the paramount role of nonmagnetic nematic fluctuations for high-temperature superconductivity in this system.


1979 ◽  
Vol 34 (3) ◽  
pp. 524 ◽  
Author(s):  
Jürgen Evers ◽  
Gilbert Oehlinger ◽  
Armin Weiss

Abstract After a high pressure -high temperature treatment of orthorhombic SrGe2 (BaSi2 type of structure) a trigonal polymorph (EuGe2 type of structure) is obtained: space group P3̄m 1; a - 410.4 pm, c - 516.5 pm; Z - 1; zGe = 0.406.


2021 ◽  
Vol 73 (03) ◽  
pp. 55-55
Author(s):  
Robert Ziegler

For the past several months, the rig count in North America has been slowly but steadily improving and some pockets of deepwater operations are finally showing some activity, especially in Central and South America and Africa, where interesting discoveries continue. Arctic operations also are picking up, though not in North America, where a new administration in the US is bringing some uncertainty to upstream operations. Looking at leasing activity in 2020, however, the operators on federal land seem to have built up a backlog, so the immediate consequences of recent executive action seem not to be significant, though they do set an important precedent. More significant seems to be the opposition to pipelines, which are the most-efficient and safest way to transport any form of bulk material, be it gas, liquid, or slurry. Even if the most-stretched targets of an energy transition become reality, the need for pipeline transport will remain, and even increase, if the gas transported is biogas and hydrogen, where much larger volumes must be transported for the same calorific value of natural gas. In my tenure as a reviewer for JPT, I had refrained from a materials-focused special simply because high-pressure/high-temperature (HP/HT) conferences and sessions seem to be dominated by them and I wanted to demonstrate a wider spectrum of the challenges of HP/HT operations. With the energy transition leading to the possibility of free hydrogen being introduced into the energy system outside of established chemical feedstock installations (which are all low-pressure), this is a good time to remind our industry (and the outside world) that vast experience exists in the oil and gas industry on the interaction of hydrogen and metal (at very high pressures), a challenge that is still not completely understood and that is still a large cause of pressure-vessel failures (e.g., in refineries). Also, if carbon dioxide is intended to be captured and contained in metal vessels, another set of metallurgical challenges emerges. This Technology Focus looks at two papers from Asia, where these challenges were discovered and mitigated, and one paper from Gulf of Mexico deepwater operations. Many learnings can be taken from these papers, and extremely costly and safety-critical failures and loss of containment can be avoided. Addressing technical risk, thorough and detailed front-end engineering is a cost-effective and cost-saving activity, and this applies especially for front-end corrosion engineering and testing, as we have seen from several megaprojects in the past where this was not done to the extent finally understood to have been required. So, I invite you all to understand and embrace the fact that sound and competent engineering, as well as communicating learnings across functions and industries, is the key enabler for future success in our stressed industry, and to use our engineering brainpower and imagination to bring those HP/HT projects currently deemed too expensive to develop within the realm of the current oil-price environment.


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