Wavelength-dependent measurements of extinction in an extended-face crystal of zinc selenide

Stevenson, Andrew W.; Barnea, Z.

doi:10.1107/s010876738300104x

Cited by 6 publications

(5 citation statements)

References 19 publications

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“…(1980), A36, 482-490] have been reanalysed with a view to explaining the unresolved discrepancies between theory and experiment present in the original analysis of the most severely extinguished reflections. The results obtained are shown to complement the recent findings of a wavelength-dependent study using the same crystal specimen [Stevenson & Barnea (1983). Acta Cryst.…”

supporting

confidence: 81%

“…If r/(2g) >> 1 but sin 20 is sufficiently small then r sin 20/(2g) ... 1, with r* depending on both r and g, and if sin 20 is very small the crystal may even be classified as type II. The authors are not aware of any studies with extended-face crystals where the sin 20 factor has been included in the extinction model [with the exception of Stevenson & Barnea (1983) -hereafter referred to as SB], making its inclusion of particular interest.'}" When primary extinction effects are important Zachariasen (1967) predicts that r* should be replaced by = r* + 3r[r-r*]/(2~.…”

Section: Discussion and Resultsmentioning

confidence: 99%

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Extinction in an extended-face crystal of zinc selenide

Stevenson¹,

Barnea²

1983

Acta Cryst Sect A

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supporting

confidence: 81%

Section: Discussion and Resultsmentioning

confidence: 99%

Extinction in an extended-face crystal of zinc selenide

Stevenson¹,

Barnea²

1983

Acta Cryst Sect A

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“…t The value of r is quite large (cf. Table 4 of Stevenson & Barnea, 1983a), as expected for such a perfect sample. We should note three points with regard to the extinction correction.…”

Section: Analysis and Resultsmentioning

confidence: 48%

Thermal vibrations and bonding in GaAs: an extended-face crystal study

Stevenson¹

1994

Acta Cryst Sect A

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Accurate X-ray integrated-intensity data collected from an extended-face crystal of GaAs are analysed to provide detailed information on the thermal vibrations of atomic species, including cubic anharmonicity, at room temperature. The values obtained for the thermal parameters are BGa = 0.622 (3) A 2, B s = 0.483(5)A 2 and ~GaAs'-" --0.6(1) X 10-18jX -3 (defined in the text). The inclusion of cubic anharmonic thermal vibrations is shown to be highly significant. In order to interpret the data collected for certain low-angle Bragg reflections for which m h + k + l = 4n + 2 (in particular, 200, 222 and 222), it is necessary to consider bonding effects. It is shown that there is a net transfer of electron charge from gallium to arsenic [Q --0.12 (3) e] and that the inclusion of bonding effects in the least-squares analysis is highly significant. The analysis includes allowance for the extremely severe extinction effects present for such a perfect sample (minimum extinction factor 0.286). The refined value of the mean radius of © 1994 International Union of Crystallography Printed in Great Britain -all rights reserved perfect-crystal domains is 4.6 (2)I~m. The final fit, for 153 independent Bragg reflections, is excellent, as indicated by the weighted R factor of 0.683% and the goodness-of-fit parameter of 1.083. The results of the least-squares analysis are compared for the cases of relativistic Hartree-Fock, Thomas-Fermi-Dirac and relativistic Dirac-Slater atomic scattering factors, the former being favoured.

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“…We have demonstrated repeatedly the remarkable advantages of using extended-face imperfect crystals for accurate measurement of relative X-ray integrated Bragg intensities even in the case of very highly absorbing crystals (Harada et al, 1970;Mair et al, 1971;McIntyre et al, 1980;Stevenson & Barnea, 1983aStevenson, 1994). Briefly, these advantages include the following:…”

Section: Absolute Intensity Measurementsmentioning

confidence: 97%

Measuring the linearity of X-ray detectors: consequences for absolute attenuation, scattering and absolute Bragg intensities

et al. 2011

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The linearity of response of X‐ray detectors is tested. Examples of linearity tests demonstrate the remarkable range of linear response of flowing‐gas ion chambers in the synchrotron environment. The diagnostic is also highly sensitive to the presence in the X‐ray beam of harmonic X‐rays diffracted by a higher‐order reflection of the monochromator. The remarkable range of linearity of ion chambers has enabled the accurate measurement of the absolute X‐ray attenuation of a number of elements. It should now be possible to measure the absolute intensity of Bragg reflections, provided such measurements are carried out with extended‐face single crystals. The advantages of the extended‐face crystal technique for Bragg intensity measurements are summarized and a number of approaches to absolute Bragg intensity measurement are discussed.

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Wavelength-dependent measurements of extinction in an extended-face crystal of zinc selenide

Cited by 6 publications

References 19 publications

Extinction in an extended-face crystal of zinc selenide

Extinction in an extended-face crystal of zinc selenide

Thermal vibrations and bonding in GaAs: an extended-face crystal study

Measuring the linearity of X-ray detectors: consequences for absolute attenuation, scattering and absolute Bragg intensities

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