摘要:

A method is presented of determining powder data from photographs. With a microphotometer the density is measured in steps of 0.01° 2θ. These data are used by a computer program. With this program the background and the noise level are determined first. After the detection of the diffraction peaks, the peak positions and intensities are refined, a suitable model for the peak profile being used. A procedure is described for scaling of several photographs. The final results are illustrated with a comparison of 2θ values determined according to this method and the calculated values of the lattice refined with these data. The resulting data prove to be equivalent to the data obtained by conventional means. The computer program is written in FORTRAN

ISSN:1600-5767    

DOI:10.1107/S0021889875009417

出版商:International Union of Crystallography    

年代:1975

数据来源: WILEY

摘要:

Some experimental and theoretical comparisons have been made of the effectiveness of four techniques which have been commonly used for monochromatizing X‐radiation for use in diffraction studies of liquids: monochromator crystals, curved or flat; β‐filter and pulse‐height analyzer; balanced dual filters. The β‐filter/pulse‐height analyzer system alone results in unacceptable error, at both low and highs(s= 4πλ−1sinθ). Dual filters can be made quite effective, actually approaching the resolution possible with monoch

ISSN:1600-5767    

DOI:10.1107/S0021889875009429

出版商:International Union of Crystallography    

年代:1975

数据来源: WILEY

摘要:

With the stable environment afforded by a dynamically pumped wet specimen chamber, the thickness of a fully hydrated protein microcrystal may be obtained in an electron microscope from an incident‐beam attenuation measurement after disappearance of the diffraction pattern. Such measurements on orthorhombic catalase crystals have been successfully cross‐correlated with thickness measurements on the same crystals made with an interference light microscope over a range from a few hundred to a few thousand Ångst

ISSN:1600-5767    

DOI:10.1107/S0021889875009430

出版商:International Union of Crystallography    

年代:1975

数据来源: WILEY

摘要:

Extinction coefficients for pure and doped single crystals of potassium chloride have been measured with the use of polarized X‐rays and subsequent analysis in terms of Zachariasen's theory of X‐ray diffraction from real crystals. The sizes of the mosaic domains and the angles of misorientation between them have been determined from the extinction coefficients corresponding to copper and cobalt radiations. It has been observed that with increase in doping the sizes of the domains diminish and the misorientation between them increa

ISSN:1600-5767    

DOI:10.1107/S0021889875009442

出版商:International Union of Crystallography    

年代:1975

数据来源: WILEY

摘要:

A set of reference intensities,ki, are required for the quantitative interpretation of X‐ray diffraction patterns of mixtures. Eachkiwas heretofore determined individually from binary mixtures of a one‐to‐one weight ratio. A procedure for the determination of allki's of interest simultaneously is presented. The X‐ray diffraction patterns of multicomponent mixtures usually contain overlapping peaks. This overlapping problem can be avoided by choosing an arbitrary reference material already present in the mixture and/or using the strongestresolvedreflections directly. These concepts are substantiated by ten examples. The maximum standard deviation of the matrix‐flushing method has been estimated to be 8%

ISSN:1600-5767    

DOI:10.1107/S0021889875009454

出版商:International Union of Crystallography    

年代:1975

数据来源: WILEY

摘要:

It was suggested [Nunes, Nathans&Schoenborn (1971).Acta Cryst. A27, 284–291] that collection of neutron diffraction data from protein crystals could be accelerated greatly by a white‐beam Laue technique (to make full use of the reactor spectrum) with Fourier time‐of‐flight analysis employed to obtain individual reflection intensities. A prototype Fourier chopper has been built. In this paper are described its construction, operation, methods of data analysis, and tests performed with a myoglobin crystal. Although the technique is proved feasible, it is of marginal value when used with a single detector. A spectrometer utilizing an extended detector array is required to realise its full po

ISSN:1600-5767    

DOI:10.1107/S0021889875009466

出版商:International Union of Crystallography    

年代:1975

数据来源: WILEY

摘要:

A stereographic projection method of analysis has been developed for analyzing the misorientation contrast of crystal subgrain boundaries which are observed in Berg–Barrett X‐ray micrographs. The boundary appearance is described in terms of the geometry of the boundary with respect to the crystal surface, the angular misorientation of the adjacent subgrains, and the X‐ray diffraction conditions. The rotation axis for the misorientation of adjacent subgrains, including the sense of the rotation, and the amount of misorientation is determined from the width and relative contrast of the boundary in various images. Experimental results are described for subgrain boundaries in zinc crystals solidified along different crystallographic growth directions. The Burgers vectors of the dislocations composing the subgrain boundary are indirectly determined by this m

ISSN:1600-5767    

DOI:10.1107/S0021889875009478

出版商:International Union of Crystallography    

年代:1975

数据来源: WILEY

摘要:

A modified geometry for a three‐circle (χ = 90°) X‐ray or neutron single‐crystal, low‐temperature diffractometer is described in which the detector is mounted on a partial vertical circle. It is shown that this extra facility permits sufficient rotation about the scattering vector to enable the effects of multiple diffraction to be detected and thu

ISSN:1600-5767    

DOI:10.1107/S002188987500948X

出版商:International Union of Crystallography    

年代:1975

数据来源: WILEY

摘要:

A means of measuring strain and lattice parameter directly in epitaxic layers by `double‐crystal' X‐ray diffraction is presented. The method described has three major advantages; that it is achieved by a simple addition to a commercial goniometer; that the area of sample illuminated is defined solely by the collimator; and that single or double‐crystal diffraction can be selected, simultaneously if needed, on exactly the same specimen

ISSN:1600-5767    

DOI:10.1107/S0021889875009491

出版商:International Union of Crystallography    

年代:1975

数据来源: WILEY

摘要:

A silicon powder Standard Reference Material, SRM‐640, has been prepared for use as a standard in powder diffractometry. Powder diffraction measurements were performed with a tungsten internal standard and a high‐angle goniometer. The measureda/λ is 3.525176. With λ(CuKα1peak) taken as 1.5405981 Å,a= 5.430880 (35) Å, uncorrected for refraction. Comparison of a with values obtained with a single‐crystal from one of the boules reveals a difference of 3 parts in 105. This difference suggests a subtle systematic error in powder diffractometry or a change in lattice spacing near crystal boundaries. Use of the SRM should permit individual measurements of lattice parameters to be made reproducible to near 1 part in 105and an absolute accuracy of at leas

ISSN:1600-5767    

DOI:10.1107/S0021889875009508

出版商:International Union of Crystallography    

年代:1975

数据来源: WILEY