Theoretical and experimental investigation of the equation of state of boron plasmas

Zhang, Shuai; Militzer, Burkhard; Gregor, M.C.; Caspersen, Kyle; Yang, Lin; Gaffney, Jim; Ogitsu, Tadashi; Swift, Damian; Lazicki, Amy; Erskine, David J.; London, Richard A.; Celliers, P. M.; Nilsen, Joseph; Sterne, P. A.; Whitley, Heather D.

doi:10.1103/physreve.98.023205

Cited by 35 publications

(54 citation statements)

References 113 publications

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“…Hence, for pressures greater than 300 GPa ( ω = 0.1), the changes of electronic structure in the sphere defined by the cutoff radius are not negligible. It means that under enough pressure, the core‐valence separation in pseudo‐potentials needs to be tailored …”

Section: Resultsmentioning

confidence: 99%

Electronic structure of first and second row atoms under harmonic confinement

Robles‐Navarro

Fuentealba

Muñoz

et al. 2019

Int J of Quantum Chemistry

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Atoms under pressure undergo a number of modifications of their electronic structure. Good examples are the spontaneous ionization, stabilization of excited‐state configurations, and contraction of atomic‐shells. In this work, we study the effects of confinement with harmonic potentials on the electronic structure of atoms from H to Ne. Dynamic and static correlation is taken into account with coupled cluster with single and double excitations and CASSCF calculations. Because the strength of harmonic confinement cannot be translated into pressure, we envisioned a “calibration” method to transform confinement into pressure. We focused on the effect of confinement on: (a) changes of electron distribution and localization within the K and L shells, (b) confinement‐induced ionization pressure, (c) level crossing of electronic states, and (d) correlation energy. We found that contraction of valence and core‐shells are not negligible and that the use of standard pseudopotentials might be not adequate to study solids under extreme pressures. The critical pressure at which atoms ionize follows a periodic trend, and it ranges from 28 GPa for Li to 10.8 TPa for Ne. In Li and Be, pressure induces mixing of the ground state configuration with excited states. At high pressure, the ground states of Li and Be become a doublet and a triplet with configurations 1s22p and 1s22s2p, respectively, which could change the chemistry of Be. Finally, it is observed that atoms with fewer electrons correlation increases, but for atoms with more electrons, the increasing of kinetic energy dominates over electron correlation.

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Section: Resultsmentioning

confidence: 99%

Electronic structure of first and second row atoms under harmonic confinement

Robles‐Navarro

Fuentealba

Muñoz

et al. 2019

Int J of Quantum Chemistry

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“…8, segments of the temperature Hugoniot curves between 20 and 500 eV and the corresponding x-ray mass attenuation coefficient µ(T ) for a 9 keV x-ray impinging on a shock-heated plasma at temperature T and compression ratio ρ/ρ 0 illustrate the theory developed herein for materials B, C, B 4 C and BN mentioned in Ref. [18]. Densities ρ 1 and ρ 2 of component ions in a two-component plasma with concentrations x 1 and x 2 and density ρ are determined by requiring that the WS volume of an average ion in the plasma is the average of the WS volumes of the constituent ions:…”

Section: Opacity: Mass Attenuation Coefficientmentioning

confidence: 56%

Opacity of shock-heated boron plasmas

Johnson

Nilsen

2019

High Energy Density Physics

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Standard measures of opacity, the imaginary part of the atomic scattering factor f 2 and the x-ray mass attenuation coefficient µ/ρ, are evaluated in shock-heated boron, boron carbide and boron nitride plasmas. The Hugoniot equation, relating the temperature T behind a shock wave to the compression ratio ρ/ρ 0 across the shock front, is used in connection with the plasma equation of state to determine the pressure p, effective plasma charge Z * and the K-shell occupation in terms of ρ/ρ 0 . Solutions of the Hugoniot equation (determined within the framework of the generalized Thomas-Fermi theory) reveal that the K-shell occupation in low-Z ions decreases rapidly from 2 to 0.1 as the temperature increases from 20eV to 500eV; a temperature range in which the shock compression ratio is near 4. The average-atom model (a quantum mechanical version of the generalized Thomas-Fermi theory) is used to determine K-shell and continuum wave functions and the photoionization cross section for x-rays in the energy range ω = 1 eV to 10 keV, where the opacity is dominated by the atomic photoionization process. For an uncompressed boron plasma at T = 10 eV, where the K-shell is filled, the average-atom cross section, the atomic scattering factor and the mass attenuation coefficient are all shown to agree closely with previous (cold matter) tabulations [1][2][3]. For shock-compressed plasmas, the dependence of µ/ρ on temperature can be approximated by scaling previously tabulated cold-matter values by the relative K-shell occupation; however, there is a relatively small residual dependence arising from the photoionization cross section. Attenuation coefficients µ for a 9 keV x-ray are given as functions of T along the Hugoniot for B, C, B 4 C and BN plasmas.

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“…Various stable and metastable polymorphs of elemental boron have been proposed as superhard [8][9][10], superconducting [11][12][13][14], and even topological materials [15]. Furthermore, because of its higher density and tensile strength as compared to plastics, this low-Z material offers an option as an ablator in inertial confinement fusion and high energy density experiments, and its phase behavior as a function of temperature and pressure is of extreme interest [16,17]. The structural chemistry of boron, including metastable phases that could be created in experiment, must be understood in order to accurately model its behavior under such conditions.…”

Section: Introductionmentioning

confidence: 99%

Structural Motifs and Bonding in Two Families of Boron Structures Predicted at Megabar Pressures

Hilleke,

Zurek,

Ogitsu

et al. 2021

Preprint

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The complex crystal chemistry of elemental boron has led to numerous proposed structures with distinctive motifs as well as contradictory findings. Herein, evolutionary structure searches performed at 100 GPa have uncovered a series of potential new metastable phases of boron, and bonding analyses were carried out to elucidate their electronic structure. These polymorphs, dynamically stable at 100 GPa, were grouped into two families. The first was derived from the thermodynamic minimum at these conditions, α-Ga, whereas channels comprised the second. Two additional intergrowth structures were uncovered, and it was shown they could be constructed by stacking layers of α-Ga-like and channel-like allotropes on top of each other. A detailed bonding analysis revealed networks of four-center σ-bonding functions linked by two-center B-B bonds in the α-Ga based structures, and networks that were largely composed of three-center σ-bonding functions in the channelbased structures. Seven of these high pressure phases were found to be metastable at atmospheric conditions, and their Vickers hardnesses were estimated to be ∼36 GPa.

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Theoretical and experimental investigation of the equation of state of boron plasmas

Cited by 35 publications

References 113 publications

Electronic structure of first and second row atoms under harmonic confinement

Electronic structure of first and second row atoms under harmonic confinement

Opacity of shock-heated boron plasmas

Structural Motifs and Bonding in Two Families of Boron Structures Predicted at Megabar Pressures

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