Neutron diffraction on subcritical and supercritical krypton

Fredrikze, H.

doi:10.1103/physreva.36.2272

Cited by 21 publications

(15 citation statements)

References 27 publications

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“…A large number of investigations have been performed in the past in a wide range of thermodynamic conditions, both using computer simulations and integral equation techniques. [4][5][6][7][8][9][10] In the present study we performed a series of constant-pressure classical Monte Carlo ͑MC͒ simulations in configuration space covering the region investigated by the experiment. This specific simulation technique was chosen because EXAFS probes only equal time structural properties which are correctly sampled in the (N, P,T) ensemble in this way.…”

Section: Local Structure Of Condensed Krypton: Computer Simulationsmentioning

confidence: 99%

High-pressure EXAFS measurements of solid and liquid Kr

et al. 1996

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X-ray-absorption measurements of liquid and solid krypton at room temperature in the pressure range 0.1-30 GPa have been performed using the dispersive setup and diamond-anvil cells as a pressure device. The evolution of the near-edge structures as a function of pressure, including the first intense resonance, has been interpreted using multiple-scattering calculations. It is shown that the near-edge structures are reproduced taking into account two-body and three-body terms associated with the first-neighbor atoms. Extended x-ray-absorption fine-structure (EXAFS) spectra have been analyzed in the framework a multiple-scattering data-analysis approach taking proper account of the atomic background including the [1s4p], [1s3d], and [1s3p] double-electron excitation channels. Isobaric Monte Carlo (MC) computer simulations based on empirical pair potentials, as proposed by Barker (K2) and Aziz (HFD-B), have been performed to make a quantitative comparison of theoretical and experimental local structural details of condensed krypton at high pressures. From the analysis of EXAFS data we were able to obtain simultaneous information on average distance, width, and asymmetry of the first-neighbor distribution, as a function of pressure. These parameters yield a unique insight on the potential function because they are affected by both minimum position and curvature of the effective pair potential. The trend of the first-neighbor distribution as a function of pressure is in quantitative agreement with the HFD-B potential at moderate pressures, deviations are found at higher pressures where EXAFS spectra are very sensitive to the hard-core repulsive part of the potential. The weak EXAFS signal of liquid krypton at room temperature and 0.75 GPa has been found in accord with the results of the MC simulations within the noise of the measurement

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Section: Local Structure Of Condensed Krypton: Computer Simulationsmentioning

confidence: 99%

High-pressure EXAFS measurements of solid and liquid Kr

et al. 1996

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“…The data were corrected for background, multiple scattering (including scattering between the sample and the container and the tail of the cryostat), attenuation effects, and effects for inelastic scattering. 14 for the compressibility theorem l5 S(n,K=0)=k B T/(dp/dn) T (11) for the four experimental densities, using the equation of state of Stewart et a/. 16 It turned out that C(n,K=0) could be represented extremely well by a linear function of the density, with the correct C(n=0, K=0) limit, whereas for //(rt,/c=0) this was not the case.…”

Section: Equations (4) and (6) Show That Hom H\(k) Co(rc) And C\(kmentioning

confidence: 99%

Pair potential from neutron diffraction on argon at low densities

et al. 1989

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“…At present, approaches based on MC simulation allow for a complete description of the scattering problem in such cases. In a recent experiment on krypton (Fredrikze, 1987) in which the scattering from the cell contributed to 30% of the total intensity, a MC technique has been applied to take into account the multiple scattering. The attenuation of the sample intensity due to the cell was calculated only for single scattering, using numerical integration.…”

Section: Discussionmentioning

confidence: 99%

“…00 O 1990 International Union of Crystallography technique a typical statistical error of 1% on the total scattered intensity is generally acceptable. However, in special cases such as diffraction from gases at high pressure where the contribution from the container exceeds 30% of the total intensity (Fredrikze, 1987) or can reach values of 80-90% (Bellissent-Funel, Buontempo, Petrillo & Ricci, 1989), an accuracy as high as 0.1% in the data reduction is needed to obtain an accuracy of a few percent in the corrected intensity due to single-scattering processes from the sample only. In these cases, the crucial point is the subtraction of the cell contribution from the measured total intensity since multiple processes taking place between sample and cell and into the cell itself, although non-negligible, represent in any case a modest contribution.…”

Section: Introductionmentioning

confidence: 99%