The structure and Bijvoet ratios of cadmium selenide

Freeman, D. K.; Mair, S. L.; Barnea, Z.

doi:10.1107/s0567739477000977

Cited by 31 publications

(28 citation statements)

References 4 publications

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“…Cromer, Larson & Roof (1964) for UMoC2. Attempts were also made to refine the dispersion corrections from observed Bijvoet ratios (Zachariasen, 1965;Freeman, Mair & Barnea, 1977). Large correlations precluded the simultaneous refinement of all four dispersion corrections, but the corrections for either atomic species could be ascertained separately (Freeman, Mair & Barnea, 1977) and showed approximate agreement with the values of Cromer & Liberman (1970) in the case of the imaginary corrections.…”

Section: Resultsmentioning

confidence: 99%

“…Attempts were also made to refine the dispersion corrections from observed Bijvoet ratios (Zachariasen, 1965;Freeman, Mair & Barnea, 1977). Large correlations precluded the simultaneous refinement of all four dispersion corrections, but the corrections for either atomic species could be ascertained separately (Freeman, Mair & Barnea, 1977) and showed approximate agreement with the values of Cromer & Liberman (1970) in the case of the imaginary corrections. The refined values of the real dispersion corrections, however, showed large discrepancies with those of Cromer & Liberman (1970), highlighting the extreme sensitivity of these quantities to the quality of the data.…”

Section: Resultsmentioning

confidence: 99%

“…The Bragg intensities were then corrected for Lorentz and polarization effects, the latter including the effect of the monochromator (Azaroff, 1955), which was assumed to follow kinematic theory (see also Freeman, Mair & Barnea, 1977). The square roots of the corrected intensities were then divided by the refined scale factor to yield the ]Foil.…”

Section: Discussionmentioning

confidence: 99%

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Anharmonic thermal vibrations and the position parameter in wurtzite structures. I. Cadmium sulphide

Stevenson¹,

Milanko²,

Barnea³

1984

Acta Crystallogr Sect B

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Intensity measurements have been carried out with an extended-face single crystal of hexagonal CdS using Mo Ka X-radiation at room temperature. The Bragg intensities were analysed by using the oneparticle potential (OPP) within the framework of Dawson's [Proc. R. Soc. London Set. A (1967), 298, [255][256][257][258][259][260][261][262][263] generalized structure-factor formulation with allowance for cubic anharmonic effects. The position parameter in the wurtzite structure which is not determined by symmetry is evaluated, and its dependence on the temperature-factor model used is demonstrated. The most reliable determination of this position parameter, with allowance for cubic anharmonicity, is 0.37715(8). The observation of significant differences between the intensities of nonsymmetry-related reflections occurring at the same Bragg angle demonstrates the possibility of measuring the anharmonicity of thermal vibrations.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Anharmonic thermal vibrations and the position parameter in wurtzite structures. I. Cadmium sulphide

Stevenson¹,

Milanko²,

Barnea³

1984

Acta Crystallogr Sect B

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“…Direct experimental determinations off" have been carried out only for a few atoms (see Table 1) by careful measurements of selected Bijvoet differences. The availability of synchrotron radiation of tunable wavelengths has led to accurate determinations off" (Phillips, Templeton, Templeton & Hodgson, 1978 Zachariasen (1965); (e) recalculated by Engel (1972); (f) 13 3 4 present work; (g) Parthasarathy (1962); (h) Templeton, Zalkin, Ruben & Templeton (1979); (i) see (h); (j) Engel & Sturm (1975); (k) Marezio (1965a); (l) Marezio, Tranqui & Capponi (1975); (m) Freeman, Mair & Barnea (1977); (n) Hall & Maslen (1966); (o) . Using a GEXRD-3 diffractometer equipped with Ross filters and a full to circle, the integrated intensities for a set of hkl, hkl and hkl, hkl reflections were collected.…”

Section: Introductionmentioning

confidence: 99%

An experimental determination of the anomalous dispersion factorf'' for sulfur

Soriano-Garcı́a¹,

Parthasarathy²

1984

Acta Cryst Sect A

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notation has the following utility. The irreducible representation with even and odd behaviour under various group elements refers to the difference structure Ci or C2. Now the average structure is of course invariant under all group elements, so that when we add it to CI or C2 to give the actual structure of the material at 00' etc. or NN' etc. in Fig. 1, the group elements with character -1 for CI or C2 are lost. Our subgroup symbol therefore remains as the space group of the material in the pure component form. This will remain unchanged if at lower temperatures the modulation wave squares up and we move out of the realm of sinusoidal modulation described by an irreducible representation. AbstractThe anomalous dispersion factor, f', of sulfur for Cu Ka radiation has been determined to be 0.60 (3) using measurements of Bijvoet differences of 175 selected reflections for a 6-(4-nitrobenzyl)thioinosine crystal.

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“…The fact that the to and 20 circles are uncoupled enables us to collect data at asymmetric settings. [The symmetric settings of a given Bragg reflection corresponding to the azimuthal angle to being 0 or 180 °, where we refer to extendedface crystal geometry (Mair, Prager & Barnea, 1971a, b;Freeman, Mair & Barnea, 1977) and align the sample normal to be accurately parallel to the diffractometer ~o axis.] In this paper we will utilize this capability of the four-circle diffractometer to collect accurate X-ray integrated intensities as a function of tO, for a number of semiconductor substrate materials and epitaxic layers.…”

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confidence: 99%

X-ray integrated intensities from semiconductor substrates and epitaxic layers – a comparison of kinematical and dynamical theories with experiment

Stevenson¹

1993

Acta Cryst Sect A

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X-ray integrated intensities have been collected from extended-face specimens as a function of azimuthal angle ~b (rotation angle about the scattering vector) with a four-circle diffractometer for a number of semiconductor substrate materials and epitaxic layers. The Bragg reflections (and X-ray wavelengths) have been chosen so that as wide a range of asymmetry as possible is encompassed. It is shown that the interpretation of these results, in terms of kinematical and perfect-crystal dynamical X-ray diffraction theories, provides a measure of the perfection of the crystal being investigated. The interpretation of some results requires consideration of extinction effects and their dependence on asymmetry. Such

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The structure and Bijvoet ratios of cadmium selenide

Cited by 31 publications

References 4 publications

Anharmonic thermal vibrations and the position parameter in wurtzite structures. I. Cadmium sulphide

Anharmonic thermal vibrations and the position parameter in wurtzite structures. I. Cadmium sulphide

An experimental determination of the anomalous dispersion factorf'' for sulfur

X-ray integrated intensities from semiconductor substrates and epitaxic layers – a comparison of kinematical and dynamical theories with experiment

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