Chemical bonding in hydrogen and lithium under pressure

Naumov, Ivan; Hemley, Russell J.; Hoffmann, Roald; Ashcroft, N. W.

doi:10.1063/1.4928076

Cited by 30 publications

(21 citation statements)

References 62 publications

(75 reference statements)

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“…Pressure-induced increase of cation coordination number is repeatedly observed tendency 38–40 that was outlined as a general rule of high-pressure crystal chemistry in reviews of Prewitt and Downs 41 and Grochala et al (2007) 27 . In inorganic oxocompounds this tendency is typically realized along with evolution of the oxygen sublattice toward the close packing arrangements 41 .…”

Section: Discussionmentioning

confidence: 87%

Penta- and hexa-coordinated beryllium and phosphorus in high-pressure modifications of CaBe2P2O8

et al. 2019

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Beryllium oxides have been extensively studied due to their unique chemical properties and important technological applications. Typically, in inorganic compounds beryllium is tetrahedrally coordinated by oxygen atoms. Herein based on results of in situ single crystal X-ray diffraction studies and ab initio calculations we report on the high-pressure behavior of CaBe 2 P 2 O 8 , to the best of our knowledge the first compound showing a step-wise transition of Be coordination from tetrahedral (4) to octahedral (6) through trigonal bipyramidal (5). It is remarkable that the same transformation route is observed for phosphorus. Our theoretical analysis suggests that the sequence of structural transitions of CaBe 2 P 2 O 8 is associated with the electronic transformation from predominantly molecular orbitals at low pressure to the state with overlapping electronic clouds of anions orbitals.

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Section: Discussionmentioning

confidence: 87%

Penta- and hexa-coordinated beryllium and phosphorus in high-pressure modifications of CaBe2P2O8

et al. 2019

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“…For example, under compression both H and Li undergo an s-p electronic transition, which leads to complex structure with low coordination numbers8910. In particular, Li, Na, and H all exhibit a maximum in their melting curves, as well as the subsequent low-temperature melting23411.…”

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confidence: 99%

Predicted reentrant melting of dense hydrogen at ultra-high pressures

Geng

2016

Sci Rep

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The phase diagram of hydrogen is one of the most important challenges in high-pressure physics and astrophysics. Especially, the melting of dense hydrogen is complicated by dimer dissociation, metallization and nuclear quantum effect of protons, which together lead to a cold melting of dense hydrogen when above 500 GPa. Nonetheless, the variation of the melting curve at higher pressures is virtually uncharted. Here we report that using ab initio molecular dynamics and path integral simulations based on density functional theory, a new atomic phase is discovered, which gives an uplifting melting curve of dense hydrogen when beyond 2 TPa, and results in a reentrant solid-liquid transition before entering the Wigner crystalline phase of protons. The findings greatly extend the phase diagram of dense hydrogen, and put metallic hydrogen into the group of alkali metals, with its melting curve closely resembling those of lithium and sodium.

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“…At sufficiently high pressure, liquid hydrogen becomes metallic. This is associated with the electronic transition from molecular H2 to atomic H [28][29] [30].…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic anomalies and three distinct liquid-liquid transitions in warm dense liquid hydrogen

Geng

Wu²,

Marqués

et al. 2019

Phys. Rev. B

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The properties of hydrogen at high pressure have wide implications in astrophysics and high-pressure physics. Its phase change in the liquid is variously described as a metallization, H2-dissociation, density discontinuity or plasma phase transition. It has been tacitly assumed that these phenomena coincide at a first-order liquid-liquid transition (LLT). In this work, the relevant pressure-temperature conditions are thoroughly explored with first-principles molecular dynamics. We show there is a large dependency on exchange-correlation functional and significant finite size effects. We use hysteresis in a number of measurable quantities to demonstrate a first-order transition up to a critical point, above which molecular and atomic liquids are indistinguishable. At higher temperature beyond the critical point, H2-dissociation becomes a smooth cross-over in the supercritical region that can be modelled by a pseudo-transition, where the H2→2H transformation is localized and does not cause a density discontinuity at metallization. Thermodynamic anomalies and counter-intuitive transport behavior of protons are also discovered even far beyond the critical point, making this dissociative transition highly relevant to the Supplementary Material. Results of dimer-dimer bond-length distribution (DDLD) calculations, comparison between PBE and vdW-DF results, the thermodynamic modelling of pseudo-transition and phase boundaries, calculated isotherms (equation of state, EOS), transient clusters and their lifetime and charge state, the angular distribution function of H3 clusters, mixing of H and H2 liquid, thermal fluctuation analysis, isotope effect, finite size effects, and the assessment of proton selfdiffusivity and viscosity.

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Chemical bonding in hydrogen and lithium under pressure

Cited by 30 publications

References 62 publications

Penta- and hexa-coordinated beryllium and phosphorus in high-pressure modifications of CaBe2P2O8

Penta- and hexa-coordinated beryllium and phosphorus in high-pressure modifications of CaBe2P2O8

Predicted reentrant melting of dense hydrogen at ultra-high pressures

Thermodynamic anomalies and three distinct liquid-liquid transitions in warm dense liquid hydrogen

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