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Nellis WJ. A Perspective on Hydrogen Near the Liquid-Liquid Phase Transition and Metallization of Fluid H. J Phys Chem Lett 2021; 12:7972-7981. [PMID: 34392677 DOI: 10.1021/acs.jpclett.1c01734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Metallic hydrogen has been a major issue in physical chemistry since its prediction in 1935. Its predicted density implies 100 GPa (106 bar = Mbar) pressures P are needed to make metallic H with the Fermi temperature TF = 220 000 K. Temperatures T can be several 1000 K and still be "very low" with T/TF ≪ 1. In 1996, metallic fluid H was made under dynamic compression at P = 140 GPa and calculated T ≈ 3000 K generated with a two-stage light-gas gun. Those T's place metallic H in the liquid-liquid phase transition region. The purpose of this Perspective is to place the phase curve measured in laser-heated diamond anvil cells in context with those measured electrical conductivities. That phase curve is probably caused by dissociation of H2 to H starting near 90 GPa/1600 K. Metallic H then forms in a crossover as a semiconductor up to 140 GPa/3000 K. Dynamic quasi-isentropic pressure was tuned to make metallic H by design in those conductivity experiments.
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Affiliation(s)
- W J Nellis
- Department of Physics, Harvard University, 17 Oxford Street, Cambridge, Massachusetts 02138, United States
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Yao B, Kuznetsov VL, Xiao T, Slocombe DR, Rao CNR, Hensel F, Edwards PP. Metals and non-metals in the periodic table. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2020; 378:20200213. [PMID: 32811363 PMCID: PMC7435143 DOI: 10.1098/rsta.2020.0213] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 06/26/2020] [Indexed: 06/11/2023]
Abstract
The demarcation of the chemical elements into metals and non-metals dates back to the dawn of Dmitri Mendeleev's construction of the periodic table; it still represents the cornerstone of our view of modern chemistry. In this contribution, a particular emphasis will be attached to the question 'Why do the chemical elements of the periodic table exist either as metals or non-metals under ambient conditions?' This is perhaps most apparent in the p-block of the periodic table where one sees an almost-diagonal line separating metals and non-metals. The first searching, quantum-mechanical considerations of this question were put forward by Hund in 1934. Interestingly, the very first discussion of the problem-in fact, a pre-quantum-mechanical approach-was made earlier, by Goldhammer in 1913 and Herzfeld in 1927. Their simple rationalization, in terms of atomic properties which confer metallic or non-metallic status to elements across the periodic table, leads to what is commonly called the Goldhammer-Herzfeld criterion for metallization. For a variety of undoubtedly complex reasons, the Goldhammer-Herzfeld theory lay dormant for close to half a century. However, since that time the criterion has been repeatedly applied, with great success, to many systems and materials exhibiting non-metal to metal transitions in order to predict, and understand, the precise conditions for metallization. Here, we review the application of Goldhammer-Herzfeld theory to the question of the metallic versus non-metallic status of chemical elements within the periodic system. A link between that theory and the work of Sir Nevill Mott on the metal-non-metal transition is also highlighted. The application of the 'simple', but highly effective Goldhammer-Herzfeld and Mott criteria, reveal when a chemical element of the periodic table will behave as a metal, and when it will behave as a non-metal. The success of these different, but converging approaches, lends weight to the idea of a simple, universal criterion for rationalizing the instantly-recognizable structure of the periodic table where …the metals are here, the non-metals are there … The challenge of the metallic and non-metallic states of oxides is also briefly introduced. This article is part of the theme issue 'Mendeleev and the periodic table'.
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Affiliation(s)
- Benzhen Yao
- KACST-Oxford Centre of Excellence in Petrochemicals, Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, UK
| | - Vladimir L. Kuznetsov
- KACST-Oxford Centre of Excellence in Petrochemicals, Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, UK
| | - Tiancun Xiao
- KACST-Oxford Centre of Excellence in Petrochemicals, Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, UK
| | - Daniel R. Slocombe
- School of Engineering, Cardiff University, Queen's Buildings, The Parade, Cardiff CF24 3AA, UK
| | - C. N. R. Rao
- New Chemistry Unit, Chemistry and Physics of Materials Unit, Theoretical Science Unit and School of Advanced Materials, Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Jakkur PO, Bangalore 560064, India
| | - Friedrich Hensel
- Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse, Marburg 35032, Germany
| | - Peter P. Edwards
- KACST-Oxford Centre of Excellence in Petrochemicals, Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, UK
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Nellis WJ. Metastable ultracondensed hydrogenous materials. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:504001. [PMID: 29111507 DOI: 10.1088/1361-648x/aa98b4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The primary purpose of this paper is to stimulate theoretical predictions of how to retain metastably hydrogenous materials made at high pressure P on release to ambient. Ultracondensed metallic hydrogen has been made at high pressures in the fluid and reported made probably in the solid. Because the long quest for metallic hydrogen is likely to be concluded in the relatively near future, a logical question is whether another research direction, comparable in scale to the quest for metallic H, will arise in high pressure research. One possibility is retention of metastable solid metallic hydrogen and other hydrogenous materials on release of dynamic and static high pressures P to ambient. If hydrogenous materials could be retained metastably on release, those materials would be a new class of materials for scientific investigations and technological applications. This paper is a review of the current situation with the synthesis of metallic hydrogen, potential technological applications of metastable metallic H and other hydrogenous materials at ambient, and general background of published experimental and theoretical work on what has been accomplished with metastable phases in the past and thus what might be accomplished in the future.
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Affiliation(s)
- W J Nellis
- Department of Physics, Harvard University, 17 Oxford Street, Cambridge, MA 02138, United States of America
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Delocalization of Electrons in Strong Insulators at High Dynamic Pressures. MATERIALS 2011; 4:1168-1181. [PMID: 28879973 PMCID: PMC5448641 DOI: 10.3390/ma4061168] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/28/2011] [Accepted: 06/13/2011] [Indexed: 11/16/2022]
Abstract
Systematics of material responses to shock flows at high dynamic pressures are discussed. Dissipation in shock flows drives structural and electronic transitions or crossovers, such as used to synthesize metallic liquid hydrogen and most probably Al2O3 metallic glass. The term “metal” here means electrical conduction in a degenerate system, which occurs by band overlap in degenerate condensed matter, rather than by thermal ionization in a non-degenerate plasma. Since H2 and probably disordered Al2O3 become poor metals with minimum metallic conductivity (MMC) virtually all insulators with intermediate strengths do so as well under dynamic compression. That is, the magnitude of strength determines the split between thermal energy and disorder, which determines material response. These crossovers occur via a transition from insulators with electrons localized in chemical bonds to poor metals with electron energy bands. For example, radial extents of outermost electrons of Al and O atoms are 7 a0 and 4 a0, respectively, much greater than 1.7 a0 needed for onset of hybridization at 300 GPa. All such insulators are Mott insulators, provided the term “correlated electrons” includes chemical bonds.
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Chau R, Mitchell AC, Minich RW, Nellis WJ. Metallization of fluid nitrogen and the mott transition in highly compressed low-Z fluids. PHYSICAL REVIEW LETTERS 2003; 90:245501. [PMID: 12857199 DOI: 10.1103/physrevlett.90.245501] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2002] [Indexed: 05/24/2023]
Abstract
Electrical conductivities are reported for degenerate fluid nitrogen at pressures up to 180 GPa (1.8 Mbar) and temperatures of approximately 7000 K. These extreme quasi-isentropic conditions were achieved with multiple-shock compression generated with a two-stage light-gas gun. Nitrogen undergoes a nonmetal-metal transition at 120 GPa, probably in the monatomic state. These N data and previous conductivity data for H, O, Cs, and Rb are used to develop a general picture of the systematics of the nonmetal-metal transition in these fluids. Specifically, the density dependences of electrical conductivities in the semiconducting fluid are well correlated with the radial extent of the electronic charge-density distributions of H, N, O, Cs, and Rb atoms. These new data for N scale with previous data for O, as expected from their similar charge-density distributions.
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Affiliation(s)
- R Chau
- Lawrence Livermore National Laboratory, University of California, Livermore, California 94550, USA
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