Optical properties of high-pressure fluid hydrogen across molecular dissociation

Optical properties of compressed fluid hydrogen in the region where dissociation and metallization is observed are computed by ab initio methods and compared with recent experimental results. We confirm that at T > 3,000 K, both processes are continuous, while at T < 1,500 K, the first-order phase transition is accompanied by a discontinuity of the dc conductivity and the thermal conductivity, while both the reflectivity and absorption coefficient vary rapidly but continuously. Our results support the recent analysis of National Ignition Facility (NIF) experiments [Celliers PM, et al. (2018) Science 361:677–682], which assigned the inception of metallization to pressures where the reflectivity is ∼0.3. Our results also support the conclusion that the temperature plateau seen in laser-heated diamond-anvil cell (DAC) experiments at temperatures higher than 1,500 K corresponds to the onset of optical absorption, not to the phase transition.

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Liquid–liquid phase transition in hydrogen by coupled electron–ion Monte Carlo simulations

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1603853113 ◽

2016 ◽

Vol 113 (18) ◽

pp. 4953-4957 ◽

Cited By ~ 59

Author(s):

Carlo Pierleoni ◽

Miguel A. Morales ◽

Giovanni Rillo ◽

Markus Holzmann ◽

David M. Ceperley

Keyword(s):

Phase Transition ◽

Monte Carlo ◽

Density Functional ◽

Fluid Phase ◽

Transition Line ◽

Energy Applications ◽

First Order Phase Transition ◽

Fundamental Research ◽

Diamond Anvil ◽

First Order Phase

The phase diagram of high-pressure hydrogen is of great interest for fundamental research, planetary physics, and energy applications. A first-order phase transition in the fluid phase between a molecular insulating fluid and a monoatomic metallic fluid has been predicted. The existence and precise location of the transition line is relevant for planetary models. Recent experiments reported contrasting results about the location of the transition. Theoretical results based on density functional theory are also very scattered. We report highly accurate coupled electron–ion Monte Carlo calculations of this transition, finding results that lie between the two experimental predictions, close to that measured in diamond anvil cell experiments but at 25–30 GPa higher pressure. The transition along an isotherm is signaled by a discontinuity in the specific volume, a sudden dissociation of the molecules, a jump in electrical conductivity, and loss of electron localization.

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The deformation mechanism of a pressure-induced phase transition in dehydrated analcime

Mineralogical Magazine ◽

10.1180/minmag.2012.076.1.129 ◽

2012 ◽

Vol 76 (1) ◽

pp. 129-142 ◽

Cited By ~ 6

Author(s):

A. Yu. Likhacheva ◽

S. V. Rashchenko ◽

Yu. V. Seryotkin

Keyword(s):

Phase Transition ◽

Equation Of State ◽

Structure Type ◽

Elastic Behaviour ◽

Structural Behaviour ◽

Synchrotron Powder Diffraction ◽

First Order Phase Transition ◽

Diamond Anvil ◽

First Order Phase ◽

Murnaghan Equation

AbstractThe elastic and structural behaviour of dehydrated analcime in compression in a non-penetrating medium up to 3 GPa was studied in a diamond anvil cell using in situ synchrotron powder diffraction. A first-order phase transition at 0.4–0.7 GPa is accompanied by a symmetry change from monoclinic (I2/a) to pseudo-rhombohedral (R3) due to trigonalization of the aluminosilicate framework. This is due to the migration of cations to new positions close to the 6-membered rings forming the channels. The reduction of the mean aperture of the structure-forming 6- and 8-membered rings, as a result of tetrahedral tilting, leads to a 7.5% reduction in volume at the phase transition. The bulk modulus values are 38(2) GPa for the low pressure (LP) phase [fitted with a Murnaghan equation of state, K' = 4 (fixed)] and 11(4) GPa for the high pressure (HP) phase [fitted with a third-order Birch–Murnaghan equation of state, K' = 9(1)]. The elastic behaviour of the LP phase is anisotropic, with compressibilities βa:βb:βc in the ratio 1:4:2; the most compressible direction b coinciding with the orientation of empty 8-membered rings. The compressibility of the HP phase is isotropic. Trigonalization appears to be the most effective (and probably unique) mechanism of radical volume contraction for the ANA structure type.

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Structural phase transition of CeAuGe at high pressure

Zeitschrift für Kristallographie - Crystalline Materials ◽

10.1524/zkri.220.2.122.59121 ◽

2005 ◽

Vol 220 (2/3) ◽

Cited By ~ 3

Author(s):

Valeri Brouskov ◽

Michael Hanfland ◽

Rainer Pöttgen ◽

Ulrich Schwarz

Keyword(s):

Phase Transition ◽

High Pressure ◽

Structural Phase ◽

Lattice Parameter ◽

First Order ◽

First Order Phase Transition ◽

Diamond Anvil ◽

Ternary Intermetallic Compound ◽

First Order Phase ◽

Type Crystal

AbstractStructural properties of the ternary intermetallic compound CeAuGe were investigated at hydrostatic pressures up to 15 GPa with high-resolution angle dispersive X-ray powder diffraction using synchrotron radiation and the diamond anvil cell technique. At 8.7(7) GPa a first order phase transition is observed from a hexagonal NdPtSb-type arrangement into an orthorhombic high-pressure modification with a TiNiSi-type crystal structure. The transformation is associated with a 3% shortening of the lattice parameter perpendicular to the puckered layers [AuGe]

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Crystal structure of the high-pressure phase of the oxonitridosilicate chloride Ce4[Si4O3 + x N7 − x ]Cl1 − x O x , x ≃ 0.2

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768106003302 ◽

2006 ◽

Vol 62 (2) ◽

pp. 205-211 ◽

Cited By ~ 1

Author(s):

Alexandra Friedrich ◽

Eiken Haussühl ◽

Wolfgang Morgenroth ◽

Alexandra Lieb ◽

Björn Winkler ◽

...

Keyword(s):

Phase Transition ◽

High Pressure ◽

Single Crystal ◽

Structural Changes ◽

Low Pressure ◽

First Order Phase Transition ◽

Compression Mechanism ◽

Diamond Anvil ◽

Structural Mechanisms ◽

First Order Phase

The structural compression mechanism of Ce4[Si4O3 + x N7 − x ]Cl1 − x O x , x ≃ 0.2, was investigated by in situ single-crystal synchrotron X-ray diffraction at pressures of 3.0, 8.5 and 8.6 GPa using the diamond–anvil cell technique. On increasing pressure the low-pressure cubic structure first undergoes only minor structural changes. Between 8.5 and 8.6 GPa a first-order phase transition occurs, accompanied by a change of the single-crystal colour from light orange to dark red. The main structural mechanisms, leading to a volume reduction of about 5% at the phase transition, are an increase in and a rearrangement of the Ce coordination, the loss of the Ce2, Ce3 split position, and a bending of some of the inter-polyhedral Si—N—Si angles in the arrangement of the corner-sharing Si tetrahedra. The latter is responsible for the short c axis of the orthorhombic high-pressure structure compared with the cell parameter of the cubic low-pressure structure.

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Surface ordering and destruction of the first order phase transition smectic A-smectic C* in free standing smectic films

Journal de Physique II ◽

10.1051/jp2:1994237 ◽

1994 ◽

Vol 4 (10) ◽

pp. 1865-1874 ◽

Cited By ~ 10

Author(s):

E. Demikhov ◽

U. Hoffmann ◽

H. Stegemeyer

Keyword(s):

Phase Transition ◽

Order Phase Transition ◽

Free Standing ◽

First Order ◽

Surface Ordering ◽

Smectic A ◽

Smectic C ◽

First Order Phase Transition ◽

First Order Phase

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Gravitational wave signals of dark matter freeze-out

Journal of High Energy Physics ◽

10.1007/jhep02(2021)022 ◽

2021 ◽

Vol 2021 (2) ◽

Cited By ~ 3

Author(s):

Danny Marfatia ◽

Po-Yan Tseng

Keyword(s):

Phase Transition ◽

Dark Matter ◽

Gravitational Waves ◽

Order Phase Transition ◽

First Order ◽

Stochastic Background ◽

First Order Phase Transition ◽

Relic Abundance ◽

First Order Phase ◽

Freeze Out

Abstract We study the stochastic background of gravitational waves which accompany the sudden freeze-out of dark matter triggered by a cosmological first order phase transition that endows dark matter with mass. We consider models that produce the measured dark matter relic abundance via (1) bubble filtering, and (2) inflation and reheating, and show that gravitational waves from these mechanisms are detectable at future interferometers.

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Dark Matter production from relativistic bubble walls

Journal of High Energy Physics ◽

10.1007/jhep03(2021)288 ◽

2021 ◽

Vol 2021 (3) ◽

Author(s):

Aleksandr Azatov ◽

Miguel Vanvlasselaer ◽

Wen Yin

Keyword(s):

Phase Transition ◽

Dark Matter ◽

Electroweak Phase Transition ◽

First Order ◽

Matter Production ◽

First Order Phase Transition ◽

Relic Abundance ◽

Higgs Portal ◽

First Order Phase ◽

Gravitational Background

Abstract In this paper we present a novel mechanism for producing the observed Dark Matter (DM) relic abundance during the First Order Phase Transition (FOPT) in the early universe. We show that the bubble expansion with ultra-relativistic velocities can lead to the abundance of DM particles with masses much larger than the scale of the transition. We study this non-thermal production mechanism in the context of a generic phase transition and the electroweak phase transition. The application of the mechanism to the Higgs portal DM as well as the signal in the Stochastic Gravitational Background are discussed.

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