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1

Digitale Medien

Equations for diffuse scattering from materials with multiple sublattices (1975)

Hayakawa, M. ; Cohen, J. B.

[S.l.] : International Union of Crystallography (IUCr)

Acta crystallographica 31 (1975), S. 635-645

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ISSN: 1600-5724

Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001

Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik

Notizen: General equations are presented for the diffuse scattering due to local ionic arrangements and displacements in systems with more than one ion per lattice point. Up to fourth-order terms are included. These are placed in a form easy to evaluate in specific cases; examples are given of a solid-solution oxide, and an oxide with vacant sites. Methods for employing these equations for the separation of the various contributions are discussed.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1107/S0567739475001362

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2

Digitale Medien

X-ray diffraction studies of Wüstite at high temperature (1975)

Hayakawa, M. ; Cohen, J. B.

Copenhagen : International Union of Crystallography (IUCr)

Applied crystallography online 8 (1975), S. 126-126

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ISSN: 1600-5767

Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001

Thema: Geologie und Paläontologie , Physik

Notizen: Diffuse scattering from FexO was measured at 840°C. Relatively sharp peaks were observed along the [h00] direction near the NaCl-type fundamental peaks.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1107/S0021889875009788

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3

Digitale Medien

Determination of single-crystal elastic constants from a cubic polycrystalline aggregate (1985)

Hayakawa, M. ; Imai, S. ; Oka, M.

Copenhagen : International Union of Crystallography (IUCr)

Applied crystallography online 18 (1985), S. 513-518

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ISSN: 1600-5767

Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001

Thema: Geologie und Paläontologie , Physik

Notizen: A method for determining cubic stiffness constants from polcrystalline Young's modulus and X-ray elastic constants is described. The relations used among these elastic constants are those based on Kröner's quasiisotropic model. The X-ray elastic constants required [S1(hkl)] are obtained by measuring various (hkl) d spacings of a stressed specimen under symmetric θ–2θ scan mode. An application to an Fe–31Ni alloy has given the results: C11 = 1.47, C12 = 1.05 and C44 = 1.24 × 1011 Pa.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1107/S0021889885010809

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4

Digitale Medien

Experimental considerations in measurements of diffuse scattering (1975)

Hayakawa, M. ; Bardhan, P. ; Cohen, J. B.

Copenhagen : International Union of Crystallography (IUCr)

Applied crystallography online 8 (1975), S. 87-95

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ISSN: 1600-5767

Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001

Thema: Geologie und Paläontologie , Physik

Notizen: A brief review is given of the Borie–Sparks method of measuring and separating the diffuse scattering in alloys due to local displacements of atoms from lattice sites. Experimental techniques are reviewed with particular emphasis on simple computer controls, dead time, monochromators and specimens. After this, sources of error in the measurements are discussed and simple methods for assessing these errors presented. Equations for estimating higher-order terms than those included by Borie and Sparks are presented. It now appears that a thorough analysis of the errors needs to be made for each measurement prior to its publication. As this kind of experiment is readily automated and easily analyzed for errors with modern computers, this should now become standard procedure. It is also suggested that intensities in electron units be kept on file and made available when requested, as is done with structure factors.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1107/S0021889875009715

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5

Digitale Medien

XPKFIT: peak separation with arbitrary relations among the component peaks (1981)

Hayakawa, M. ; Oka, M.

Copenhagen : International Union of Crystallography (IUCr)

Applied crystallography online 14 (1981), S. 145-148

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ISSN: 1600-5767

Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001

Thema: Geologie und Paläontologie , Physik

Notizen: A computer program for the separation of a composite peak into the components and the background has been written in Fortran. Each component is approximated by a function of the form y(x) = c [1 + ({{x - d}\over{e}})^{2}]^{-f}, where c, d, e and f are the parameters to be determined by a least-squares method. Arbitrary, known or assumed relations among the parameters of different components may be read in to reduce the number of independent parameters and save computation time or, in other cases, to offer a better chance of separating a complex composite peak by varying a subset of the parameters.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1107/S0021889881008984

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6

Digitale Medien

Errors in quantitative analysis of diffuse scattering from alloys (1973)

Gragg, J. E. ; Hayakawa, M. ; Cohen, J. B.

Copenhagen : International Union of Crystallography (IUCr)

Applied crystallography online 6 (1973), S. 59-66

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ISSN: 1600-5767

Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001

Thema: Geologie und Paläontologie , Physik

Notizen: Errors in separating diffuse scattering resulting from local order from that from static and dynamic displacements have been examined; the Borie–Sparks symmetry procedure was employed, which includes second-order terms in the displacements. The largest source of error when X-rays are employed is the variation in the ratio of scattering factors across the volume measured in reciprocal space. Large errors in the Warren local-order parameters result for clustering systems with displacement terms of the same order as the local-order parameters (or larger), but not if the size terms are smaller. For systems with local order the errors in these parameters are small. Uncertainties in the size terms are always appreciable. Other errors that were considered are: higher-order terms, extrapolation under Bragg peaks, errors in Compton scattering, background and surface roughness, and uncertainties in composition or polarization resulting from a monochromator.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1107/S0021889873008162

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