Growth and crystal structures of solid xenon and krypton

Sonnenblick, Y.; Kálmán, Z. H.; Steinberger, I. T.

doi:10.1016/0022-0248(82)90221-4

Cited by 17 publications

(9 citation statements)

References 27 publications

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“…The solid phase of Ar and Kr in Vycor, just below the freezing temperature, is not consistent with the bulk structure due to the lack of the (200). The diffraction pattern is also inconsistent with an hcp structure, which is energetically very close to the fcc [15][16][17], differing only in the layer stacking order, and has been observed in a metastable state in vapor deposited crystals [18].…”

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confidence: 91%

“…The broad peaks of the dhcp structure are still present in the low temperature phase, indicating a coexistence of the fcc and dhcp structures. Kr and Xe grown by vapor deposition below about 0.65T f exhibited coexistence of the hcp and fcc phases [18], while above this temperature only the fcc structure existed. In this case, the hcp structure is frozen into the quench condensed solid since the atoms lack the mobility at low temperature to anneal into the stable fcc structure.…”

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confidence: 95%

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New Disorder Induced Phase Transitions of Classical Rare Gases in Porous Vycor Glass

1998

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We report the results of x-ray diffraction studies of Ar and Kr confined in Vycor glass. The freezing and melting temperatures of both Ar and Kr were suppressed well below their bulk freezing points. On solidification, both samples crystallized in a disordered hexagonal close packed structure similar to that observed in molecular dynamics simulations of confined solids. A new solid-solid phase transition is observed at a reduced temperature of T ͞T f ഠ 0.5 when confined to Vycor. Below this temperature the disordered hexagonal closed packed structure coexists with the fcc structure.[S0031-9007 (98)06675-7] PACS numbers: 61.43.Gt, 61.10.NzThe effects of finite size and confinement on gases, liquids, and solids adsorbed in mesoporous materials, such as porous glasses and zeolites, is a topic of current interest for classical and quantum systems. For example, in classical systems the liquid-gas transition is enhanced with respect to the bulk [1,2] while the liquid-solid transition is suppressed [2,3]. Hysteresis, which appears to be a stable thermodynamic behavior, is also introduced into these transitions. Quantum transitions show equally dramatic behavior. For example, the superfluid transition of 4 He in Vycor is substantially suppressed while the critical exponents remain unchanged. However, confinement in aerogel results in only a small suppression but substantially different critical exponents [4,5]. 3 He, on the other hand, has superfluid phases in high porosity aerogels [6,7], but not in lower porosity confining geometries.Microscopic structural studies of materials confined to mesoporous media have only recently been undertaken, and a variety of different behaviors have been reported. In some cases, such as Hg in Vycor [8], the structure of the confined solid is identical to that of the bulk while in other cases, such as H 2 O and D 2 in Vycor [9,10], confinement stabilizes new structures not present in the bulk. Confinement can also suppress crystalline order, such as O 2 in xerogel [11], resulting in a glassy solid phase. Confinement has not, however, been observed to introduce new phase transitions in any systems that have been studied to date.In this Letter, we report x-ray diffraction studies of Ar and Kr adsorbed in Vycor. As in many other systems, a suppression of the liquid-solid transition hysteresis between freezing and melting is observed. On freezing, both Ar and Kr are observed to form a disordered hexagonal close packed (dhcp) structure, characterized by random plane stacking, in contrast to the bulk fcc structure. A new phase transition, which is absent from the bulk phase diagram, occurs at roughly half of the freezing temperature below which both Kr and Ar exhibit coexistence of the dhcp and fcc phases. This solid-solid structural phase transition is repeatable on cycling and no appreciable hysteresis is observed. Thus, the coexistence phase appears to be a true disorder-induced thermodynamic phase, rather than a metastable phase.The confining media used in these studies was Vycor glass. Vy...

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New Disorder Induced Phase Transitions of Classical Rare Gases in Porous Vycor Glass

1998

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“…There was no dependence of T 1 on the isotopic composition of the xenon, indicating no presence of bulk paramagnetic relaxation in ice. Future experimental work should include a lower temperature range T 1 study (4-50 K) on ice and snow [49], purposely introducing oxygen prior to and post solid formation in temperature dependent runs, and growing single-crystal solid Xe [37,50] to potentially reach an upper limit of 129 Xe T 1 in efforts to better understand the spin-rotation coupling strength.…”

Section: Discussionmentioning

confidence: 99%

Robust solidXe129longitudinal relaxation times

Limes

Sorte

et al. 2016

Phys. Rev. B

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We find that if solid xenon is formed from liquid xenon, denoted "ice", there is a 10% increase of 129 Xe longitudinal relaxation T1 time (taken at 77 K and 2 Tesla) over a trickle-freeze formation, denoted "snow". Forming xenon ice also gives unprecedented reproducibility of 129 Xe T1 measurements across a range of 77-150 K. This temperature dependence roughly follows the theory of spin-rotation mediated by Raman scattering of harmonic phonons (SRRS), though it results in a smaller-than-predicted spin-rotation coupling strength cK0/h. Enriched ice 129 Xe T1 experiments show no isotopic dependence in bulk relaxation mechanisms at 77 K and at kilogauss fields.

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“…Other techniques as x rays or neutron diffraction are more suitable to get structural information directly, but these methods are sensitive to the long-range order in the matrix rather than to the local environment around the molecular impurity. [1][2][3] X-ray absorption is another way to obtain structural information about the environment: as a matter of fact, the x-ray absorption spectra are deeply modified when going from the gas phase to the condensed phase and are sensitive to the nearest neighbors surrounding the absorbing atom. The low-frequency part of the spectrum is called XANES ͑X-ray Absorption Near-Edge Structure͒ and contains information about the electronic structure, while the high-frequency part of the spectrum is called EXAFS ͑Extended X-ray Absorption Fine Structure͒ and gives directly the distances between the absorbing atom and its neighbors.…”

Section: Introductionmentioning

confidence: 99%

EXAFS studies of the trapping site structure for molecules isolated in cryogenic matrices

Roubin¹,

Varin²,

Crépin

et al. 2000

Low Temperature Physics

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We present here results concerning the first attempt of determining the trapping site structure of molecules isolated in inert matrices at low temperature by the EXAFS (Extended X-ray Absorption Fine Structure) method. The experiments have been performed at the K edge of argon, silicon, sulfur, and chlorine for pure solid argon, and for SiH4, OCS, and HCl isolated in different cryogenic matrices. The EXAFS technique is sensitive to the local environment around the absorbing atom, and the spectral features induced by the matrix material (Ar, Xe, N2, and CH4) are clearly evidenced here. The data allow a characterization of the double substitutional site for OCS in argon and xenon, while no structure can be determined for the accommodation of SiH4 in argon. A discussion of the best choice for the guest/host system to obtain a good EXAFS signal is included.

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Growth and crystal structures of solid xenon and krypton

Cited by 17 publications

References 27 publications

New Disorder Induced Phase Transitions of Classical Rare Gases in Porous Vycor Glass

New Disorder Induced Phase Transitions of Classical Rare Gases in Porous Vycor Glass

Robust solidXe129longitudinal relaxation times

EXAFS studies of the trapping site structure for molecules isolated in cryogenic matrices

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