scholarly journals New possible candidate structure for phase IV of solid hydrogen

RSC Advances ◽  
2020 ◽  
Vol 10 (44) ◽  
pp. 26443-26450
Author(s):  
Guo-Jun Li ◽  
Yun-Jun Gu ◽  
Zhi-Guo Li ◽  
Qi-Feng Chen ◽  
Xiang-Rong Chen
Keyword(s):  
Solid Hydrogen ◽  
Experimental Results ◽  
Candidate Structure ◽  
Phase Iv

As a whole, the vibron frequencies of the Ama2 structure agree better with the experimental results compared with the Pc structure.

An anomaly in the specific heat below 3 °K of copper containing hydrogen

1969 ◽  
Vol 47 (14) ◽  
pp. 1485-1491 ◽  
Author(s):  
Neil Waterhouse
Keyword(s):  
Specific Heat ◽  
Molecular Hydrogen ◽  
Pure Copper ◽  
Solid Hydrogen ◽  
Rotational State ◽  
Experimental Results ◽  
Ortho Hydrogen ◽  
Temperature Range ◽  
A Value ◽  
Heat Curve

The specific heat of copper heated in hydrogen at 1040 °C has been measured over the temperature range 0.4 to 3.0 °K and found to be anomalous. The anomaly occurs in the same temperature range as the solid hydrogen λ anomaly which, in conjunction with evidence of ortho to para conversion of hydrogen in the sample, suggests the presence of molecular hydrogen in the copper. The anomaly reported by Martin for "as-received" American Smelting and Refining Company (ASARCO) 99.999+ % pure copper has been briefly compared with the present results. The form of the anomaly produced by the copper-hydrogen specimen has been compared with Schottky curves using the simplest possible model, that for two level splitting of the degenerate J = 1 rotational state of the ortho-hydrogen molecule.Maintenance of the copper-hydrogen sample at ~20 °K for approximately 1 week removed the "hump" in the specific heat curve. An equation of the form Cp = γT + (464.34/(θ0c)3)T3 was found to fit these experimental results and produced a value for γ which had increased over that for vacuumannealed pure copper by ~2%.

Crystal structure of high-pressure phase-IV solid hydrogen sulfide

1998 ◽  
Vol 57 (10) ◽  
pp. 5699-5703 ◽  
Author(s):  
S. Endo ◽  
A. Honda ◽  
K. Koto ◽  
O. Shimomura ◽  
T. Kikegawa ◽  
...  
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Hydrogen Sulfide ◽  
Solid Hydrogen ◽  
High Pressure Phase ◽  
Pressure Phase ◽  
Phase Iv

scholarly journals Dynamical effects in solid hydrogen and hydrogen-deuterium mixtures at elevated pressures.

2014 ◽  
Vol 70 (a1) ◽  
pp. C899-C899
Author(s):  
Ioan Magdau ◽  
Ross Howie ◽  
Graeme Ackland ◽  
Eugene Gregoryanz
Keyword(s):  
Raman Spectra ◽  
High Pressures ◽  
Elevated Temperatures ◽  
Melting Curve ◽  
Solid Hydrogen ◽  
Raman Signal ◽  
True Nature ◽  
Point Energy ◽  
Hydrogen Deuterium ◽  
Phase Iv

We employed molecular dynamics simulations together with some novel theoretical techniques to calculate finite temperature Raman spectra in both hydrogen (H) and hydrogen-deuterium (HD) mixtures. By conditioning the simulations with the experimental data, we have discovered the true nature of Phase IV in solid hydrogen. X-ray and neutron diffraction measurements are virtually impossible in current state of the art experiments. The experimental investigation, thus, relies mainly on spectroscopic methods which provide minimal data about crystallography. Extensive work done so far [1] has led to an impressive amount of Raman and IR data up to pressures of almost 400 GPa. By carefully investigating the positions and widths of the peaks, they discovered phase IV of solid hydrogen and mapped out the melting curve up to very high pressures. Phase IV is only stable at elevated temperatures and therefore static relaxation calculations cannot reproduce the correct crystal structure. Previous theoretical work has predicted a class of exotic crystal structures with alternating layers of different character: B (well-defined molecules) and G (poorly-defined molecules) [2] that could qualitatively describe the Raman signal. By means of MD simulations we show that at high temperature, the Pc structure acquires higher symmetry which is sufficient to reproduce the exact position of the Raman peaks. It had been suggested that in a mixed hydrogen-deuterium alloy, the heavier atoms would segregate in the B layers which would decrease the overall zero-point energy and stabilise the Pc structure. Joining efforts with the experimental team we thoroughly investigated this problem. We found no evidence of isotopic layer segregation, but our theoretical model correctly described the Raman spectra found experimentally. We concluded that the phase boundaries in HD mixtures are slightly offset which we attribute to the inhomogeneous mass effect on the temperature of the broken symmetries, but the general behaviour is similar to that of solid hydrogen. We uncovered a new effect in HD, namely mass induced phonon localization. Matching experimental and theoretical results in this respect are yet another validation of the crystallographic conformation of phase IV.

scholarly journals Candidate structure for the H2 -PRE phase of solid hydrogen

2021 ◽  
Vol 104 (21) ◽  
Author(s):  
Tom Ichibha ◽  
Yunwei Zhang ◽  
Kenta Hongo ◽  
Ryo Maezono ◽  
Fernando A. Reboredo
Keyword(s):  
Solid Hydrogen ◽  
Candidate Structure

scholarly journals Robust Diffusive Proton Motions in Phase IV of Solid Hydrogen

2014 ◽  
Vol 118 (22) ◽  
pp. 11902-11905 ◽  
Author(s):  
Hanyu Liu ◽  
John Tse ◽  
Yanming Ma
Keyword(s):  
Solid Hydrogen ◽  
Phase Iv

Diagnostics of Gold Laser Plasmas

1988 ◽  
Vol 102 ◽  
pp. 357-360
Author(s):  
J.C. Gauthier ◽  
J.P. Geindre ◽  
P. Monier ◽  
C. Chenais-Popovics ◽  
N. Tragin ◽  
...  
Keyword(s):  
Experimental Results ◽  
Pure Gold ◽  
Electronic Temperature ◽  
X Ray ◽  
Laser Plasmas ◽  
Collisional Radiative Model ◽  
Radiative Model

AbstractIn order to achieve a nickel-like X ray laser scheme we need a tool to determine the parameters which characterise the high-Z plasma. The aim of this work is to study gold laser plasmas and to compare experimental results to a collisional-radiative model which describes nickel-like ions. The electronic temperature and density are measured by the emission of an aluminium tracer. They are compared to the predictions of the nickel-like model for pure gold. The results show that the density and temperature can be estimated in a pure gold plasma.

Observation of Phase Contrast Images in STEM and CTEM Modes by Using 100 kV Field Emission Electron Gun

1974 ◽  
Vol 32 ◽  
pp. 390-391
Author(s):  
Y. Harada ◽  
T. Goto ◽  
H. Koike ◽  
T. Someya
Keyword(s):  
Field Emission ◽  
Phase Contrast ◽  
Image Formation ◽  
Fresnel Diffraction ◽  
Experimental Results ◽  
Electron Gun ◽  
Scanning Microscopy ◽  
Emission Electron ◽  
Lattice Images

Since phase contrasts of STEM images, that is, Fresnel diffraction fringes or lattice images, manifest themselves in field emission scanning microscopy, the mechanism for image formation in the STEM mode has been investigated and compared with that in CTEM mode, resulting in the theory of reciprocity. It reveals that contrast in STEM images exhibits the same properties as contrast in CTEM images. However, it appears that the validity of the reciprocity theory, especially on the details of phase contrast, has not yet been fully proven by the experiments. In this work, we shall investigate the phase contrast images obtained in both the STEM and CTEM modes of a field emission microscope (100kV), and evaluate the validity of the reciprocity theory by comparing the experimental results.

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