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Matter and Radiation at Extremes
Contents
2022
Volume: 7 Issue 3
8 Article(s)
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High Pressure Physics and Materials Science
A novel square planar N
4
2−
ring with aromaticity in BeN
4
Jiani Lin, Fangxu Wang, Qi Rui, Jianfu Li, Qinglin Wang, and Xiaoli Wang
A structural search leads to the prediction of a novel alkaline earth nitride BeN4 containing a square planar N42- ring. This compound has a particular chemical bonding pattern giving it potential as a high-energy-density material. The P4/nmm phase of BeN4 may be stable under ambient conditions, with a bandgap of 3.72
A structural search leads to the prediction of a novel alkaline earth nitride BeN
4
containing a square planar N
4
2-
ring. This compound has a particular chemical bonding pattern giving it potential as a high-energy-density material. The
P
4/
nmm
phase of BeN
4
may be stable under ambient conditions, with a bandgap of 3.72 eV. It is predicted to have high thermodynamic and kinetic stability due to transfer of the outer-shell
s
electrons of the Be atom to the N
4
cluster, with the outer-shell 2
p
orbital accommodating the lone-pair electrons of N
4
2-
. The total of six
π
electrons is the most striking feature, indicating that the square planar N
4
2-
exhibits aromaticity. Under ambient conditions, BeN
4
has a high energy density (3.924 kJ/g relative to Be
3
N
2
and N
2
gas), and its synthesis might be possible at pressures above 31.6 GPa..
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Matter and Radiation at Extremes
Publication Date: Jan. 01, 1900
Vol. 7, Issue 3, 038401 (2022)
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High-energy-density metal nitrides with armchair chains
Jianan Yuan, Kang Xia, Chi Ding, Xiaomeng Wang, Qing Lu, and Jian Sun
Polymeric nitrogen has attracted much attention owing to its possible application as an environmentally safe high-energy-density material. Based on a crystal structure search method accelerated by the use of machine learning and graph theory and on first-principles calculations, we predict a series of metal nitrides wi
Polymeric nitrogen has attracted much attention owing to its possible application as an environmentally safe high-energy-density material. Based on a crystal structure search method accelerated by the use of machine learning and graph theory and on first-principles calculations, we predict a series of metal nitrides with chain-like polynitrogen (
P
2
1
-AlN
6
,
P
2
1
-GaN
6
,
P
-1-YN
6
, and
P
4/
mnc
-TiN
8
), all of which are estimated to be energetically stable below 40.8 GPa. Phonon calculations and
ab initio
molecular dynamics simulations at finite temperature suggest that these nitrides are dynamically stable. We find that the nitrogen in these metal nitrides can polymerize into two types of poly-
N
4
2
-
chains, in which the
π
electrons are either extended or localized. Owing to the presence of the polymerized N
4
chains, these metal nitrides can store a large amount of chemical energy, which is estimated to range from 4.50 to 2.71 kJ/g. Moreover, these compounds have high detonation pressures and detonation velocities, exceeding those of conventional explosives such as TNT and HMX..
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Matter and Radiation at Extremes
Publication Date: Jan. 01, 1900
Vol. 7, Issue 3, 038402 (2022)
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Equations of state of iron and nickel to the pressure at the center of the Earth
Naohisa Hirao, Yuichi Akahama, and Yasuo Ohishi
Synchrotron radiation x-ray diffraction investigations of iron (Fe) and nickel (Ni) are conducted at pressures up to 354 and 368 GPa, respectively, and the equations of state (EOSs) at 298 K for the two elements are obtained for data extending to pressures as high as those at the center of the Earth, using the latest P
Synchrotron radiation x-ray diffraction investigations of iron (Fe) and nickel (Ni) are conducted at pressures up to 354 and 368 GPa, respectively, and the equations of state (EOSs) at 298 K for the two elements are obtained for data extending to pressures as high as those at the center of the Earth, using the latest Pt-EOS pressure scale. From a least-squares fit to the Vinet equation using the observed pressure–volume data, the isothermal bulk modulus
K
0
and its pressure derivative
K
0
′
are estimated to be 159.27(99) GPa and 5.86(4) for hcp-Fe, and 173.5(1.4) GPa and 5.55(5) for Ni. By comparing the present EOSs and extrapolated EOSs reported in the literature for Fe and Ni, the volumes of Fe and Ni at 365 GPa are found to be 2.3% and 1.5% larger than those estimated from extrapolated EOSs in previous studies, respectively. It is concluded that these discrepancies are due to the pressure scale. The present results suggest that the densities of Fe and Ni at a pressure of 365 GPa corresponding to the center of the Earth are 2.3% and 1.5%, respectively, lower than previously thought..
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Matter and Radiation at Extremes
Publication Date: Jan. 01, 1900
Vol. 7, Issue 3, 038403 (2022)
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Pressure-induced reemergence of superconductivity in BaIr
2
Ge
7
and Ba
3
Ir
4
Ge
16
with cage structures
Cuiying Pei, Tianping Ying, Yi Zhao, Lingling Gao, Weizheng Cao, Changhua Li, Hideo Hosono, and Yanpeng Qi
Clathrate-like or caged compounds have attracted great interest owing to their structural flexibility, as well as their fertile physical properties. Here, we report the pressure-induced reemergence of superconductivity in BaIr2Ge7 and Ba3Ir4Ge16, two new caged superconductors with two-dimensional building blocks of cag
Clathrate-like or caged compounds have attracted great interest owing to their structural flexibility, as well as their fertile physical properties. Here, we report the pressure-induced reemergence of superconductivity in BaIr
2
Ge
7
and Ba
3
Ir
4
Ge
16
, two new caged superconductors with two-dimensional building blocks of cage structures. After suppression of the ambient-pressure superconducting (SC-I) states, new superconducting (SC-II) states emerge unexpectedly, with
T
c
increased to a maximum of 4.4 and 4.0 K for BaIr
2
Ge
7
and Ba
3
Ir
4
Ge
16
, respectively. Combined with high-pressure synchrotron x-ray diffraction and Raman measurements, we propose that the reemergence of superconductivity in these caged superconductors can be ascribed to a pressure-induced phonon softening linked to cage shrinkage..
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Matter and Radiation at Extremes
Publication Date: Jan. 01, 1900
Vol. 7, Issue 3, 038404 (2022)
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Inertial Confinement Fusion Physics
Ultrafast probing of plasma ion temperature in proton–boron fusion by nuclear resonance fluorescence emission spectroscopy
T.-T. Qin, W. Luo, H.-Y. Lan, and W.-M. Wang
Aneutronic fusion reactions such as proton–boron fusion could efficiently produce clean energy with quite low neutron doses. However, as a consequence, conventional neutron spectral methods for diagnosing plasma ion temperature would no longer work. Therefore, finding a way to probe the ion temperature in aneutronic fu
Aneutronic fusion reactions such as proton–boron fusion could efficiently produce clean energy with quite low neutron doses. However, as a consequence, conventional neutron spectral methods for diagnosing plasma ion temperature would no longer work. Therefore, finding a way to probe the ion temperature in aneutronic fusion plasmas is a crucial task. Here, we present a method to realize ultrafast
in situ
probing of
11
B ion temperature for proton–boron fusion by Doppler broadening of the nuclear resonance fluorescence (NRF) emission spectrum. The NRF emission is excited by a collimated, intense γ-ray beam generated from submicrometer wires irradiated by a recently available petawatt (PW) laser pulse, where the γ-ray beam generation is calculated by three-dimensional particle-in-cell simulation. When the laser power is higher than 1 PW, five NRF signatures of a
11
B plasma can be clearly identified with high-resolution γ-ray detectors, as shown by our Geant4 simulations. The correlation between the NRF peak width and
11
B ion temperature is discussed, and it is found that NRF emission spectroscopy should be sensitive to
11
B ion temperatures
T
i
> 2.4 keV. This probing method can also be extended to other neutron-free-fusion isotopes, such as
6
Li and
15
N..
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Matter and Radiation at Extremes
Publication Date: Jan. 01, 1900
Vol. 7, Issue 3, 035901 (2022)
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Numerical performance assessment of double-shell targets for Z-pinch dynamic hohlraum
Y. Y. Chu, Z. Wang, J. M. Qi, Z. P. Xu, and Z. H. Li
A Z-pinch dynamic hohlraum can create the high-temperature radiation field required by indirect-drive inertial confinement fusion. A dynamic hohlraum with peak radiation temperature over 300 eV can be obtained with a >50 MA Z-pinch driver according to the scaling law of dynamic hohlraum radiation temperature vs driv
A Z-pinch dynamic hohlraum can create the high-temperature radiation field required by indirect-drive inertial confinement fusion. A dynamic hohlraum with peak radiation temperature over 300 eV can be obtained with a
>
50 MA Z-pinch driver according to the scaling law of dynamic hohlraum radiation temperature vs drive current. Based on a uniform 300 eV radiation temperature profile with a width of 10 ns, three double-shell capsules with radii of 2, 2.5, and 3 mm are proposed, and the corresponding fusion yields from a one-dimensional calculation are 28.8, 56.1, and 101.6 MJ. The implosion dynamics of the 2.5 mm-radius capsule is investigated in detail. At ignition, the areal density of the fuel is about 0.53 g/cm
2
, the fuel pressure is about 80 Gbar, and the central ion temperature is about 4.5 keV, according to the one-dimensional simulation. A two-dimensional simulation indicates that the double-shell capsule can implode nearly spherically when driven by the radiation field of a Z-pinch dynamic hohlraum. The sensitivities of the fusion performance to the radiation temperature profiles and to deviations in the capsule parameter are investigated through one-dimensional simulation, and it is found that the capsule fusion yields are rather stable in a quite large parameter space. A one-dimensional simulation of a capsule embedded in 50 mg/cm
3
CH foam indicates that the capsule performance does not change greatly in the mimicked environment of a Z-pinch dynamic hohlraum. The double-shell capsules designed here are also applicable to laser indirect-drive inertial fusion, if a laser facility can produce a uniform 300 eV radiation field and sustain it for about 10 ns..
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Matter and Radiation at Extremes
Publication Date: Jan. 01, 1900
Vol. 7, Issue 3, 035902 (2022)
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Radiation and Hydrodynamics
A molecular dynamics study of laser-excited gold
Jacob M. Molina, and T. G. White
The structural evolution of laser-excited systems of gold has previously been measured through ultrafast MeV electron diffraction. However, there has been a long-standing inability of atomistic simulations to provide a consistent picture of the melting process, leading to large discrepancies between the predicted thres
The structural evolution of laser-excited systems of gold has previously been measured through ultrafast MeV electron diffraction. However, there has been a long-standing inability of atomistic simulations to provide a consistent picture of the melting process, leading to large discrepancies between the predicted threshold energy density for complete melting, as well as the transition between heterogeneous and homogeneous melting. We make use of two-temperature classical molecular dynamics simulations utilizing three highly successful interatomic potentials and reproduce electron diffraction data presented by Mo
et al.
[Science
360
, 1451–1455 (2018)]. We recreate the experimental electron diffraction data, employing both a constant and temperature-dependent electron–ion equilibration rate. In all cases, we are able to match time-resolved electron diffraction data, and find consistency between atomistic simulations and experiments, only by allowing laser energy to be transported away from the interaction region. This additional energy-loss pathway, which scales strongly with laser fluence, we attribute to hot electrons leaving the target on a timescale commensurate with melting..
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Matter and Radiation at Extremes
Publication Date: Jan. 01, 1900
Vol. 7, Issue 3, 036901 (2022)
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Triggering star formation: Experimental compression of a foam ball induced by Taylor–Sedov blast waves
B. Albertazzi, P. Mabey, Th. Michel, G. Rigon, J. R. Marquès, S. Pikuz, S. Ryazantsev, E. Falize, L. Van Box Som, J. Meinecke, N. Ozaki, G. Gregori, and M. Koenig
The interaction between a molecular cloud and an external agent (e.g., a supernova remnant, plasma jet, radiation, or another cloud) is a common phenomenon throughout the Universe and can significantly change the star formation rate within a galaxy. This process leads to fragmentation of the cloud and to its subsequent
The interaction between a molecular cloud and an external agent (e.g., a supernova remnant, plasma jet, radiation, or another cloud) is a common phenomenon throughout the Universe and can significantly change the star formation rate within a galaxy. This process leads to fragmentation of the cloud and to its subsequent compression and can, eventually, initiate the gravitational collapse of a stable molecular cloud. It is, however, difficult to study such systems in detail using conventional techniques (numerical simulations and astronomical observations), since complex interactions of flows occur. In this paper, we experimentally investigate the compression of a foam ball by Taylor–Sedov blast waves, as an analog of supernova remnants interacting with a molecular cloud. The formation of a compression wave is observed in the foam ball, indicating the importance of such experiments for understanding how star formation is triggered by external agents..
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Matter and Radiation at Extremes
Publication Date: Jan. 01, 1900
Vol. 7, Issue 3, 036902 (2022)
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High Pressure Physics and Materials Science
Inertial Confinement Fusion Physics
Radiation and Hydrodynamics