Symmetry Breaking in Dense Solid Hydrogen: Mechanisms for the Transitions to Phase II and Phase III

Tolédano, Pierre; Katzke, Hannelore; Goncharov, Alexander F.; Hemley, Russell J.

doi:10.1103/physrevlett.103.105301

Cited by 22 publications

(21 citation statements)

References 31 publications

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“…The HCP hexagonal structure of Phase I is highlighted in red (left). Structurally speaking, the phase transition can be well distinguished paying attention to the differences in the arrangement of the molecules at 1 GPa (single molecules as rotors), and the arrangement at 45 GPa (the distribution is aligned and the rotation are restricted), in agreement with the results of Toledano et al [13]. displacement, independently of temperature, was obtained for a lattice constant of 0.7a, which appoints at the same time to the minimal energy state (Figure 1, right).…”

Section: Ifsa 2011supporting

confidence: 80%

“…It shows four images: bottom pictures are projections for all the molecules on the YZ plane, where you can observe a much more pronounced phase difference for the 1 GPa test. In that case, (Figure 2, left), projection is a circle, ie the molecules are free rotors, while in the case of 45 GPa (Figure 2, right), there is an alignment of molecules with restricted rotation, according to the image proposed by different authors [7,13]. Top of the figure shows the projections on the XY plane.…”

Section: Results and Validation Of Methodologymentioning

confidence: 99%

“…Comparison is possible through the theoretical model and predictions from Toledano et al [13]. Different experimental works discuss the transition from Phase I to Phase II of the hydrogen, that jumps from a configuration with molecules as free rotors (the atoms can describe a sphere), to an order where such rotations are restricted [7,15,16].…”

Section: Results and Validation Of Methodologymentioning

confidence: 99%

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Structural properties of hydrogen isotopes in solid phase in the context of inertial confinement fusion

Guerrero

Cuesta‐López

Perlado

2013

EPJ Web of Conferences

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Abstract. Quality of Deuterium-Tritium capsules is a critical aspect in Inertial Confinement Fusion. In this work, we present a Quantum Molecular Dynamics methodology able to model hydrogen isotopes and their structural molecular organisation at extreme pressures and cryogenic temperatures (< 15 K). Our study sets up the basis for a future analysis on the mechanical and structural properties of DT-ice in inertial confinement fusion (ICF) target manufacturing conditions.

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Section: Ifsa 2011supporting

confidence: 80%

Section: Results and Validation Of Methodologymentioning

confidence: 99%

Section: Results and Validation Of Methodologymentioning

confidence: 99%

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Structural properties of hydrogen isotopes in solid phase in the context of inertial confinement fusion

Guerrero

Cuesta‐López

Perlado

2013

EPJ Web of Conferences

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“…3,[16][17][18] A variety of theoretical techniques have been employed to explore the structures of phases II and III (see, e.g., Refs. 6,10,12,[19][20][21] ); however, the interpretation of these studies has been extensively debated. The experimental findings 22 of the incommensurate nature of phase II of solid deuterium has introduced additional difficulties into the structural solution of phase II of solid hydrogen.…”

Section: Introductionmentioning

confidence: 99%

Room-temperature structures of solid hydrogen at high pressures

Liu

Zhu

Cui

et al. 2012

The Journal of Chemical Physics

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By employing first-principles metadynamics simulations, we explore the 300 K structures of solid hydrogen over the pressure range 150-300 GPa. At 200 GPa, we find the ambient-pressure disordered hexagonal close-packed (hcp) phase transited into an insulating partially ordered hcp phase (po-hcp), a mixture of ordered graphene-like H 2 layers and the other layers of weakly coupled, disordered H 2 molecules. Within this phase, hydrogen remains in paired states with creation of shorter intra-molecular bonds, which are responsible for the very high experimental Raman peak above 4000 cm -1 . At 275 GPa, our simulations predicted a transformation from po-hcp into the ordered molecular metallic Cmca phase (4 molecules/cell) that was previously proposed to be stable only above 400 GPa. Gibbs free energy calculations at 300 K confirmed the energetic stabilities of the po-hcp and metallic Cmca phases over all known structures at 220-242 GPa and >242 GPa, respectively.Our simulations highlighted the major role played by temperature in tuning the phase stabilities and provided theoretical support for claimed metallization of solid hydrogen below 300 GPa at 300 K.2

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“…Equivalent measurements by neutron scattering require large samples, which currently are not possible to create at the needed high-pressure conditions with currently available techniques (32). Measurements of the vibron by Raman and IR spectroscopy have therefore served as key diagnostics of the state of dense hydrogen up to megabar pressures (7,30), most recently for the crystal structures of the higher pressure molecular phases (33).…”

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confidence: 99%

Bonding changes in hot fluid hydrogen at megabar pressures

Subramanian

Goncharov

Struzhkin

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Raman spectroscopy in laser-heated diamond anvil cells has been employed to probe the bonding state and phase diagram of dense hydrogen up to 140 GPa and 1,500 K. The measurements were made possible as a result of the development of new techniques for containing and probing the hot, dense fluid, which is of fundamental importance in physics, planetary science, and astrophysics. A pronounced discontinuous softening of the molecular vibron was found at elevated temperatures along with a large broadening and decrease in intensity of the roton bands. These phenomena indicate the existence of a state of the fluid having significantly modified intramolecular bonding. The results are consistent with the existence of a pressure-induced transformation in the fluid related to the presence of a temperature maximum in the melting line as a function of pressure.diamond anvil cell | high pressure | Raman scattering | laser heating | melting T he response of the covalent bond of molecular hydrogen to chemical, density, and thermal perturbations is central to a broad range of problems in the physical sciences. In particular, information on the behavior of hydrogen at very high pressures and variable temperatures is needed to explore the theoretically predicted molecular-atomic transition in the solid (1), the existence of an expanded stability field of the fluid and novel lowtemperature diffusive states (2-4), and the nature of reported transitions in the fluid at megabar pressures (5, 6). Hydrogen is also important for understanding the behavior of materials in general at extreme conditions (7,8). Hydrogen is the most abundant element in the cosmos, and the nature of hydrogen at high temperatures and pressures is crucial for understanding the interiors of large gaseous planets, including exoplanets, and other astrophysical bodies (9, 10). The latter includes detailing the sequence of transitions associated with the onset of nuclear processes in ultrahigh density hydrogen plasmas inside very large astrophysical bodies.There are numerous questions surrounding the behavior of dense hydrogen in the condensed matter domain of megabar (10 11 Pa) pressures and of order 10 3 K temperatures. Experiments and first-principles calculations indicate a temperature maximum in the melting curve as a function pressure near 100 GPa and 1,000 K (11-14). Near 140 GPa and higher temperatures, there is evidence for onset of electrical conductivity (5) and an increase in density (6). The downturn in the melting line has been predicted in various calculations, but the degree of ionization and dissociation in the molecular fluid and an onset of electrical conductivity at higher temperature vary among calculations (15)(16)(17)(18)(19)(20). Characterizing the bonding state of the dense, hot fluid under these conditions is required to search for molecular dissociation and to test competing mechanisms for the onset of electrical conductivity (6,15,17,20,21). The theoretical and experimental indications of a presence of the maximum in the melting line (11,...

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Symmetry Breaking in Dense Solid Hydrogen: Mechanisms for the Transitions to Phase II and Phase III

Cited by 22 publications

References 31 publications

Structural properties of hydrogen isotopes in solid phase in the context of inertial confinement fusion

Structural properties of hydrogen isotopes in solid phase in the context of inertial confinement fusion

Room-temperature structures of solid hydrogen at high pressures

Bonding changes in hot fluid hydrogen at megabar pressures

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