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X-ray scattering measurements of dissociation-induced metallization of dynamically compressed deuterium.

Davis P, Döppner T, Rygg JR, Fortmann C, Divol L, Pak A, Fletcher L, Becker A, Holst B, Sperling P, Redmer R, Desjarlais MP, Celliers P, Collins GW, Landen OL, Falcone RW, Glenzer SH - Nat Commun (2016)

Bottom Line: Because of applications to planetary science, inertial confinement fusion and fundamental physics, its high-pressure properties have been the subject of intense study over the past two decades.Here we present spectrally resolved x-ray scattering measurements from plasmons in dynamically compressed deuterium.Combined with Compton scattering, and velocity interferometry to determine shock pressure and mass density, this allows us to extract ionization state as a function of compression.

View Article: PubMed Central - PubMed

Affiliation: University of California, Berkeley, California 94720, USA.

ABSTRACT
Hydrogen, the simplest element in the universe, has a surprisingly complex phase diagram. Because of applications to planetary science, inertial confinement fusion and fundamental physics, its high-pressure properties have been the subject of intense study over the past two decades. While sophisticated static experiments have probed hydrogen's structure at ever higher pressures, studies examining the higher-temperature regime using dynamic compression have mostly been limited to optical measurement techniques. Here we present spectrally resolved x-ray scattering measurements from plasmons in dynamically compressed deuterium. Combined with Compton scattering, and velocity interferometry to determine shock pressure and mass density, this allows us to extract ionization state as a function of compression. The onset of ionization occurs close in pressure to where density functional theory-molecular dynamics (DFT-MD) simulations show molecular dissociation, suggesting hydrogen transitions from a molecular and insulating fluid to a conducting state without passing through an intermediate atomic phase.

No MeSH data available.


Related in: MedlinePlus

Reflectivity and conductivity calculated from DFT-MD simulations.(a) Reflectivities along the principal Hugoniot curve for 808 nm from the experiments of Celliers et al. (black diamonds) and DFT-MD calculations in this work (solid black line). Reflectivities for 532 nm from the experiments of Loubeyre et al. in hydrogen (red dots) and deuterium (red triangles) and DFT-MD calculations in this work (solid red line). (b) Dynamic electrical conductivity at the five experimental points for which the thermodynamic states along the principal Hugoniot curve are given in the legend. The dc limit (ω→0) is displayed in the inset.
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f7: Reflectivity and conductivity calculated from DFT-MD simulations.(a) Reflectivities along the principal Hugoniot curve for 808 nm from the experiments of Celliers et al. (black diamonds) and DFT-MD calculations in this work (solid black line). Reflectivities for 532 nm from the experiments of Loubeyre et al. in hydrogen (red dots) and deuterium (red triangles) and DFT-MD calculations in this work (solid red line). (b) Dynamic electrical conductivity at the five experimental points for which the thermodynamic states along the principal Hugoniot curve are given in the legend. The dc limit (ω→0) is displayed in the inset.

Mentions: To facilitate further comparison between our simulations and experimental results, optical reflectivity and dynamic conductivity were calculated from the DFT-MD results. Figure 7a shows reflectivity calculated along the principal Hugoniot (Supplementary Fig. 7 and Supplementary Note 1). Comparisons are made at 808 nm with the results of Celliers et al.19 and at 532 nm with the recent measurements by Loubeyre et al.51. Good agreement is found between experiment and theory. Between 20 and 50 GPa, DFT-MD is seen to produce somewhat higher reflectivities than the Loubeyre results, attributable to the fact that DFT-MD underestimates the bandgap systematically using exchange-correlation functionals like that of Perdew, Burke, and Ernzerhof (ref. 52), leading to early bandgap closure and an earlier onset of dissociation and, thereby, conduction. In Fig. 7b, the dynamic conductivity along the Hugoniot is plotted at a pressure range corresponding to our experimental conditions. The DC limit is plotted in the inset, showing that conductivity starts at very small values near 0.1 S m−1 at 2.8 × compression (black curve), rising orders of magnitude to a metallic conductivity of 105 S m−1 near fourfold compression (yellow curve). This confirms the continuous transition from an insulating molecular fluid to a metallic degenerate electron liquid observed in the experiments.


X-ray scattering measurements of dissociation-induced metallization of dynamically compressed deuterium.

Davis P, Döppner T, Rygg JR, Fortmann C, Divol L, Pak A, Fletcher L, Becker A, Holst B, Sperling P, Redmer R, Desjarlais MP, Celliers P, Collins GW, Landen OL, Falcone RW, Glenzer SH - Nat Commun (2016)

Reflectivity and conductivity calculated from DFT-MD simulations.(a) Reflectivities along the principal Hugoniot curve for 808 nm from the experiments of Celliers et al. (black diamonds) and DFT-MD calculations in this work (solid black line). Reflectivities for 532 nm from the experiments of Loubeyre et al. in hydrogen (red dots) and deuterium (red triangles) and DFT-MD calculations in this work (solid red line). (b) Dynamic electrical conductivity at the five experimental points for which the thermodynamic states along the principal Hugoniot curve are given in the legend. The dc limit (ω→0) is displayed in the inset.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4835540&req=5

f7: Reflectivity and conductivity calculated from DFT-MD simulations.(a) Reflectivities along the principal Hugoniot curve for 808 nm from the experiments of Celliers et al. (black diamonds) and DFT-MD calculations in this work (solid black line). Reflectivities for 532 nm from the experiments of Loubeyre et al. in hydrogen (red dots) and deuterium (red triangles) and DFT-MD calculations in this work (solid red line). (b) Dynamic electrical conductivity at the five experimental points for which the thermodynamic states along the principal Hugoniot curve are given in the legend. The dc limit (ω→0) is displayed in the inset.
Mentions: To facilitate further comparison between our simulations and experimental results, optical reflectivity and dynamic conductivity were calculated from the DFT-MD results. Figure 7a shows reflectivity calculated along the principal Hugoniot (Supplementary Fig. 7 and Supplementary Note 1). Comparisons are made at 808 nm with the results of Celliers et al.19 and at 532 nm with the recent measurements by Loubeyre et al.51. Good agreement is found between experiment and theory. Between 20 and 50 GPa, DFT-MD is seen to produce somewhat higher reflectivities than the Loubeyre results, attributable to the fact that DFT-MD underestimates the bandgap systematically using exchange-correlation functionals like that of Perdew, Burke, and Ernzerhof (ref. 52), leading to early bandgap closure and an earlier onset of dissociation and, thereby, conduction. In Fig. 7b, the dynamic conductivity along the Hugoniot is plotted at a pressure range corresponding to our experimental conditions. The DC limit is plotted in the inset, showing that conductivity starts at very small values near 0.1 S m−1 at 2.8 × compression (black curve), rising orders of magnitude to a metallic conductivity of 105 S m−1 near fourfold compression (yellow curve). This confirms the continuous transition from an insulating molecular fluid to a metallic degenerate electron liquid observed in the experiments.

Bottom Line: Because of applications to planetary science, inertial confinement fusion and fundamental physics, its high-pressure properties have been the subject of intense study over the past two decades.Here we present spectrally resolved x-ray scattering measurements from plasmons in dynamically compressed deuterium.Combined with Compton scattering, and velocity interferometry to determine shock pressure and mass density, this allows us to extract ionization state as a function of compression.

View Article: PubMed Central - PubMed

Affiliation: University of California, Berkeley, California 94720, USA.

ABSTRACT
Hydrogen, the simplest element in the universe, has a surprisingly complex phase diagram. Because of applications to planetary science, inertial confinement fusion and fundamental physics, its high-pressure properties have been the subject of intense study over the past two decades. While sophisticated static experiments have probed hydrogen's structure at ever higher pressures, studies examining the higher-temperature regime using dynamic compression have mostly been limited to optical measurement techniques. Here we present spectrally resolved x-ray scattering measurements from plasmons in dynamically compressed deuterium. Combined with Compton scattering, and velocity interferometry to determine shock pressure and mass density, this allows us to extract ionization state as a function of compression. The onset of ionization occurs close in pressure to where density functional theory-molecular dynamics (DFT-MD) simulations show molecular dissociation, suggesting hydrogen transitions from a molecular and insulating fluid to a conducting state without passing through an intermediate atomic phase.

No MeSH data available.


Related in: MedlinePlus