Cryogenic implementation of charging diamond anvil cells with H2 and D2

Ichimaru

Einaga

et al. 2015

Sci Rep

Self Cite

107

We investigated the phase transformation of hot dense fluid hydrogen using static high-pressure laser-heating experiments in a laser-heated diamond anvil cell. The results show anomalies in the heating efficiency that are likely to be attributed to the phase transition from a diatomic to monoatomic fluid hydrogen (plasma phase transition) in the pressure range between 82 and 106 GPa. This study imposes tighter constraints on the location of the hydrogen plasma phase transition boundary and suggests higher critical point than that predicted by the theoretical calculations.

Section: Methodsmentioning

confidence: 99%

Phase boundary of hot dense fluid hydrogen

Ichimaru

Einaga

et al. 2015

Sci Rep

Self Cite

107

“…Experiments were carried out by using DACs. A small piece of Li ( 7 Li, 99.95% purity, Johnson Matthey) was loaded in a sample chamber of a gasket in a DAC, and the remaining room of the sample chamber was filled with liquid H 2 by using a cryogenic loading system . We prepared two samples with the Li to H 2 molar ratios of about 1 : 6 (sample no.…”

Section: Methodsmentioning

confidence: 99%

Lithium polyhydrides synthesized under high pressure and high temperature

Matsuoka

Kuno

et al. 2017

J Raman Spectroscopy

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Polyhydrides of alkali metals under high pressures have been attracting great interests owing to the predicted pressure‐stabilized untraditional stoichiometries and potential superconductivity. We have performed Raman scattering measurements of lithium polyhydrides synthesized under high pressure and high temperature conditions up to 182 GPa. Between 30 and 180 GPa, four phases appear, and they are tentatively named α (30–140 GPa), β (30–90 GPa), γ (90–140 GPa), and δ (140 GPa) phase. By observing the H2 vibrons at higher wavenumbers than pure H2 and their pressure dependence, it was revealed that the α phase contains electrically neutral H2 in its crystal lattice without electron transfer from Li atoms. The comparisons with H2‐containing rare gas compounds Ar(H2)2, Kr(H2)4, and Xe(H2)8 suggest that a H2 molecule is surrounded by six to eight neighboring H2 molecules in the α phase. On the other hand, the Raman spectra of the β, γ, and δ phases suggest that they contain the elongated H2 that is negatively charged by the electron transferred from the surrounding matrices. All the α, β, γ, and δ phases were found to remain transparent insulators at pressures below 182 GPa. Copyright © 2017 John Wiley & Sons, Ltd.

“…A ruby ball was additionally used in run #2. We then loaded hydrogen using a liquid hydrogen‐introducing system at temperatures below 20 K [ Chi et al ., ]. The sample and hydrogen were compressed under low temperature and subsequently restored to room temperature.…”

Section: Experimental Methodsmentioning

confidence: 99%

Compression of Fe–Si–H alloys to core pressures

Tagawa

Geophysical Research Letters

Hirose

et al. 2016

Self Cite

We examined the compression behavior of hexagonal‐close‐packed (hcp) (Fe0.88Si0.12)1H0.61 and (Fe0.88Si0.12)1H0.79 (in atomic ratio) alloys up to 138 GPa in a diamond anvil cell (DAC). While contradicting experimental results were previously reported on the compression curve of double‐hcp (dhcp) FeHx (x ≈ 1), our data show that the compressibility of hcp Fe0.88Si0.12Hx alloys is very similar to those of hcp Fe and Fe0.88Si0.12, indicating that the incorporation of hydrogen into iron does not change its compression behavior remarkably. The present experiments suggest that the inner core may contain up to 0.47 wt % hydrogen (FeH0.26) if temperature is 5000 K. The calculated density profile of Fe0.88Si0.12H0.17 alloy containing 0.32 wt % hydrogen in addition to geochemically required 6.5 wt % silicon matches the seismological observations of the outer core, supporting that hydrogen is an important core light element.