摘要:

A structural refinement of ammonium hydrogen tartrate, C4H9NO6, has been completed from data obtained on an Enraf–Nonius CAD‐4 X‐ray diffractometer equipped with a Si(Li) solid‐state detector. The refinement has given comparable results with those found in the literature. A comparative study of a select number of weak reflections obtained from this study and from the results of an analysis using a conventional scintillation system indicates that the peak‐to‐background ratio is better for intensity data collected on an X‐ray diffractometer using a Si(Li) solid‐state detector system. An important application of a Si(Li) energy‐dispersive system is X‐ray fluorescence analysis which can be performed on the same single‐crystal employed in X‐ray diffraction data collection. Qualitative determinations and quantiative data on relative percentages of metal constituents have been obtained from single crystals of Lu(OH)3and Mn3[Co(CN)6]2.12H2O

ISSN:1600-5767    

DOI:10.1107/S0021889879012449

出版商:International Union of Crystallography    

年代:1979

数据来源: WILEY

摘要:

The filter theory allows one to compare the efficiencies of smoothing procedures widely used in the field of small‐angle X‐ray scattering. This method is demonstrated for polynomial fitting and modified frequency filtering. Optimized and objective smoothing parameters are determined for both procedures through the knowledge of variance reduction factors, transfer functions of the filters, the largest value of the spatial frequencies of the scattering curve and the distortions caused by the smoothing procedures. The comparison of the efficiency of polynomial fitting and frequency filtering clearly shows the superiority of the latter; therefore, this method has to be prefer

ISSN:1600-5767    

DOI:10.1107/S0021889879012450

出版商:International Union of Crystallography    

年代:1979

数据来源: WILEY

摘要:

A recent experiment on neutron diffraction by microscopically curved silicon crystals has shown the existence of the Fankuchen effect, which is a space condensation of neutrons occurring for this kind of crystal. This paper reports an experimental analysis of neutron focusing in the Fankuchen effect for curved crystals. The focusing effect in a symmetrical geometry was also investigated for comparison. The results are discussed and a conclusion is derived concerning a gain in neutron current density for the Fankuchen geometry, particularly interesting for neutron diffractometry of small biological crystals.

ISSN:1600-5767    

DOI:10.1107/S0021889879012462

出版商:International Union of Crystallography    

年代:1979

数据来源: WILEY

摘要:

The design, operating principles and constructional details of a goniometer for use in ultra‐high‐resolution objective‐lens pole‐pieces are described. Image‐matching of experimental and computer‐simulated high‐resolution electron micrographs is used to demonstrate an instrumental resolution of 1.6 Å,

ISSN:1600-5767    

DOI:10.1107/S0021889879012474

出版商:International Union of Crystallography    

年代:1979

数据来源: WILEY

摘要:

Lattice fringe and diffraction observations of hematite/ magnetite interfaces are described: elongated laths of magnetite, with (111)Mand (11)Mparallel to (0001)Hand, less frequently, (211)Mand (11)Mparallel to (0001)H, were found. In general, the interfaces are incoherent as shown by the presence of steps, which are probably transformation dislocations. The magnetite is invariably multiply twinned, showing steps which may be twinning dislocations. A theoretical analysis of the possible secondary and ternary orientation relationships due to multiple twinning explains one of the two further less‐frequent relationships indicated by texture goniometry. Such higher‐order relations are not topotaxic and their identification and interpretation is a general problem for texture goniome

ISSN:1600-5767    

DOI:10.1107/S0021889879012486

出版商:International Union of Crystallography    

年代:1979

数据来源: WILEY

摘要:

The aims of this investigation were to optimize the construction geometry of a Guinier camera, and to find a profile model useful for powder refinement work. A computer simulation of all possible directions for individually diffracted X‐rays was used to generate line profiles for a number of different situations. The influence of variations in camera geometry and specimen form are discussed. Microdensitometer data for a test film are compared with calculated profiles. An extension of the present method, which uses non‐continuous arrays, to the use of continuous functions to describe the profiles is discus

ISSN:1600-5767    

DOI:10.1107/S0021889879012498

出版商:International Union of Crystallography    

年代:1979

数据来源: WILEY

摘要:

Gas‐flame specimen‐heating equipment has been designed and constructed for structural investigations of materials which are not chemically affected by exposure to the combustion gas. The heating equipment is attachable to any standard four‐circle diffractometer, preserving all the functions of the diffractometer, and provides specimen temperatures up to 2600 K. The ventilation of the hot exhaust gas and the use of a small flame prevent the elevation of temperature at any part of the diffractometer. The maintenance of high temperatures is controlled by constant gas flow and the temperature is stable within ± 15 K at temperatures between 1800 and 2600 K. The intensity data of anα‐Al2O3single‐crystal were successfully co

ISSN:1600-5767    

DOI:10.1107/S0021889879012504

出版商:International Union of Crystallography    

年代:1979

数据来源: WILEY

摘要:

A quantitative technique is described for determining the direction of preferred orientation and the orientation distribution function of collagen fibrils in connective tissues from high‐angle X‐ray diffraction patterns. In principle, the direction of preferred orientation is parallel to the orientation of the meridian on the diffraction pattern; in practice, the orientation of the equator, which is perpendicular to the meridian and is more clearly defined, is used to deduce this direction. The angular dependence of the equatorial intensity distribution is measured at a convenient radius on a pattern. The same measurements are made on a pattern from elastoidin spicules, which consist of effectively perfectly oriented collagen molecules. Deconvolution of the former by the latter yields the orientation distribution function. This deconvolution is achieved in Fourier‐transform space where the equivalent operation is simply division; inverse transformation yields the required result. Measurements and analysis were performed with a program written for the Joyce Loebl Magiscan Image Analysis S

ISSN:1600-5767    

DOI:10.1107/S0021889879012516

出版商:International Union of Crystallography    

年代:1979

数据来源: WILEY

摘要:

The hexagonal cell dimensionsaandcof 2H‐MoS2and 2H‐WSe2have been measured over the temperature range 10 to 320 K. In both compoundsaincreased linearly andcnon‐linearly with temperature, the linear coefficient of thermal expansion in thecdirection being greater than that in the a direction for 2H‐MoS2. In 2H‐WSe2the linear coefficients of thermal expansion in theaandcdirections were approximat

ISSN:1600-5767    

DOI:10.1107/S0021889879012528

出版商:International Union of Crystallography    

年代:1979

数据来源: WILEY

摘要:

CH3(CH2)4OC6H4N: N(O)C6H4O(CH2)4CH3, C22H30N2O3; triclinic,P1 orP,Z= 2;a= 19.78,b= 9.49,c= 7.92 Å;α= 47.7,β= 120.5 andγ= 1

ISSN:1600-5767    

DOI:10.1107/S002188987901253X

出版商:International Union of Crystallography    

年代:1979

数据来源: WILEY