Molecular models for WH6 under pressure

Labet, Vanessa; Hoffmann, Roald; Ashcroft, N. W.

doi:10.1039/c1nj20560a

Cited by 11 publications

(9 citation statements)

References 49 publications

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“…124 Structure searches coupled with first-principles calculations showed that the WH, WH 2 , WH 4 and WH 6 stoichiometries become thermodynamically and dynamically stable under pressure. 123,125,126 A WH stoichiometry with P6 3 /mmc symmetry was found to have the lowest enthalpy of formation between 25 and 150 GPa, 123,125 and its structure was consistent with the experimental X-ray diffraction peaks, which were indicative of an hcp WH phase. Further experiments showed that above 50 GPa WH uptakes hydrogen such that the H : M ratio approaches 1 1 3 , 123 but higher hydrides have not yet been synthesized.…”

Section: Unintended Reactionssupporting

confidence: 67%

Predicting crystal structures and properties of matter under extreme conditions via quantum mechanics: the pressure is on

Zurek

Grochala

2015

Phys. Chem. Chem. Phys.

114

107

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Experimental studies of compressed matter are now routinely conducted at pressures exceeding 1 mln atm (100 GPa) and occasionally at pressures greater than 10 mln atm (1 TPa). The structure and properties of solids that have been so significantly squeezed differ considerably from those of solids at ambient pressure (1 atm), often leading to new and unexpected physics. Chemical reactivity is also substantially altered in the extreme pressure regime. In this feature paper we describe how synergy between theory and experiment can pave the road towards new experimental discoveries. Because chemical rules-of-thumb established at 1 atm often fail to predict the structures of solids under high pressure, automated crystal structure prediction (CSP) methods are increasingly employed. After outlining the most important CSP techniques, we showcase a few examples from the recent literature that exemplify just how useful theory can be as an aid in the interpretation of experimental data, describe exciting theoretical predictions that are guiding experiment, and discuss when the computational methods that are currently routinely employed fail. Finally, we forecast important problems that will be targeted by theory as theoretical methods undergo rapid development, along with the simultaneous increase of computational power.

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Section: Unintended Reactionssupporting

confidence: 67%

Predicting crystal structures and properties of matter under extreme conditions via quantum mechanics: the pressure is on

Zurek

Grochala

2015

Phys. Chem. Chem. Phys.

114

107

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“…136 Moreover, computational experiments hinted that WH 6 has the ability to polymerize at ambient conditions. 139 Phonon calculations confirmed that all of these phases were dynamically stable at 150 GPa. Only WH and WH 2 were found to be good metals, whereas the Fermi level of WH 4 and WH 6 lay in a pseudogap.…”

Section: Group 6: Chromium Molybdenum Tungstenmentioning

confidence: 76%

“…within) inspired the computational search for high hydrides of tungsten in the solid state at 1 atm and under pressure. 136,139 Some of the phases predicted are illustrated in Fig. 6.…”

Section: Group 6: Chromium Molybdenum Tungstenmentioning

confidence: 99%

The Search for Superconductivity in High Pressure Hydrides

Zarifi

Terpstra

et al. 2019

Reference Module in Chemistry, Molecular Sciences and Chemical Engineering

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The computational and experimental exploration of the phase diagrams of binary hydrides under high pressure has uncovered phases with novel stoichiometries and structures, some which are superconducting at quite high temperatures. Herein we review the plethora of studies that have been undertaken in the last decade on the main group and transition metal hydrides, as well as a few of the rare earth hydrides at pressures attainable in diamond anvil cells. The aggregate of data shows that the propensity for superconductivity is dependent upon the species used to "dope" hydrogen, with some of the highest values obtained for elements that belong to the alkaline and rare earth, or the pnictogen and chalcogen families.

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“…In a separate publication we discuss in detail the molecular tungsten hydrides and an unusual extended metastable structure of WH 6 stoichiometry [18].…”

Section: Molecular Tungsten Hydridesmentioning

confidence: 99%

“…We also investigated the stability of WH 6 extended structures based on aggregates of molecular WH 6 , identified in matrix experiments [13,14]. The details are given elsewhere [18]; briefly no molecular solids survive at any pressure. The molecular monomers spontaneously polymerize into extended structures during the optimization process.…”

Section: Whmentioning

confidence: 99%

WH_nunder pressure

Zaleski‐Ejgierd

Labet

Strobel

et al. 2012

J. Phys.: Condens. Matter

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An initial observation of the formation of WH under pressure from W gaskets surrounding hydrogen in diamond anvil cells led to a theoretical study of tungsten hydride phases. At P = 1 atm no stoichiometry is found to be stable with respect to separation into the elements, but as the pressure is raised WH(n) (n = 1-6, 8) stoichiometries are metastable or stable. WH and WH(4) are calculated to be stable at P > 15 GPa, WH(2) becomes stable at P > 100 GPa and WH(6) at P > 150 GPa. In agreement with experiment, the structure computed for WH is anti-NiAs. WH(2) shares with WH a hexagonal arrangement of tungsten atoms, with hydrogen atoms occupying octahedral and tetrahedral holes. For WH(4) the W atoms are in a distorted fcc arrangement. As the number of hydrogens rises, the coordination of W by H increases correspondingly, leading to a twelve-coordinated W in WH(6). In WH(8) H(2) units also develop. All of the hydrides considered should be metallic at high pressure, though the Fermi levels of WH(4) and WH(6) lie in a deep pseudogap. Prodded by these theoretical studies, experiments were then undertaken to seek phases other than WH, exploring a variety of experimental conditions that would favor further reaction. Though a better preparation and characterization of WH resulted, no higher hydrides have as yet been found.

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Molecular models for WH6 under pressure

Cited by 11 publications

References 49 publications

Predicting crystal structures and properties of matter under extreme conditions via quantum mechanics: the pressure is on

Predicting crystal structures and properties of matter under extreme conditions via quantum mechanics: the pressure is on

The Search for Superconductivity in High Pressure Hydrides

WH_nunder pressure

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Molecular models for WH6 under pressure

Cited by 11 publications

References 49 publications

Predicting crystal structures and properties of matter under extreme conditions via quantum mechanics: the pressure is on

Predicting crystal structures and properties of matter under extreme conditions via quantum mechanics: the pressure is on

The Search for Superconductivity in High Pressure Hydrides

WHnunder pressure

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Product

Resources

About

WH_nunder pressure