The Reciprocal Space as a Space of Diffraction Patterns

2009 ◽  
Vol 42 (2) ◽  
pp. 295-301 ◽  
Author(s):  
Norbert Stribeck ◽  
Ulrich Nöchel

On the basis of the concept of Polanyi [Z. Phys.(1921),7, 149–180], the mapping of fiber diffraction patterns into reciprocal space is revisited. The result is a set of concise mapping relations that does not contain any approximations. This set permits the design of a direct method that, in principle, does not require refinement of mapping parameters even for patterns of tilted fibers. The method is unsuitable for diffuse scattering patterns. If inaccuracies of two pixels can be tolerated, a pattern is automatically mapped into reciprocal space in real time. The method is proposed for the processing of the extensive sets of patterns that are recorded in time-resolved wide-angle X-ray diffraction investigations of polymer materials.


2000 ◽  
Vol 56 (4) ◽  
pp. 639-647 ◽  
Author(s):  
Massimo Nespolo ◽  
Giovanni Ferraris ◽  
Hiroshi Takeda

The X-ray investigation (precession method) of the Ruiz Peak oxybiotite, which is well known for the occurrence of a large number of polytypes and twins, revealed two complex diffraction patterns, which cannot be identified as long-period polytypes. These patterns are analysed in terms of the minimal rhombus, a geometrical asymmetric unit in reciprocal space which permits the decomposition of the composite reciprocal lattice of a twin or allotwin into the reciprocal lattices of the individuals. Both the recorded patterns correspond to a 1M–2M 1 allotwin: the relative rotation between the individuals is 120° in one case and 60° in the other. The geometrical criteria for evaluating the presence of twinning or allotwinning are analysed through these two natural examples.


1988 ◽  
Vol 02 (01) ◽  
pp. 131-146 ◽  
Author(s):  
XUDONG FAN ◽  
L. A. BURSILL ◽  
JU LIN PENG

Elementary properties of spiral lattices are evaluated in reciprocal space. The relative merits of direct space object data, Fourier transforms and power spectra (diffraction patterns) are discussed and applied to the identification of the radial law for three distinct naturally-occurring spiral structures.


Author(s):  
A. G. Jackson ◽  
J. Park ◽  
D. Wood ◽  
S. LeClair

An application of self-adaptive algorithms to TEM is presented. Analysis of diffraction patterns is an integral part of an experiment because of the need to control contrast conditions. Obtaining two-beam conditions or locating a zone axis can be time consuming or not possible, because of restrictions in the tilt ranges of the holder being used. The present approach is to manually search reciprocal space in the instrument to find zones of interest and that are accessible, visually identify the zone axis, or, analyze the patterns and plot on a stereogram the locations of major zones. Once the experimenter has plotted the orientation, then locating desired zone axes is accomplished by manually tilting. This process can be relatively easy, as in the case of a cubic crystal, or very difficult as in the the cases of hexagonal, trigonal, triclinic, monoclinic or orthorhombic crystals, particularly when the crystalline region is a few microns or less in size.


Crystals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 192 ◽  
Author(s):  
Xinfu Gu

Reproducible crystallographic features between new phase and matrix are often observed during phase transformation, including orientation relationship, interfacial orientation, morphology, and so on. The geometrical matching in the interface is the key to understanding the preferred transformation crystallography. Recently, a new geometrical method emphasizing the atomic row matching in the interface, the so-called near row matching method, has been proposed to predict the preferred orientations between two arbitrary crystals. In this work, this method originally expressed in direct space was further extended to the reciprocal space. These two methods were implemented in our free software PTClab (version 1.19). It is found that these two expressions are nearly equivalent. As the near row matching in reciprocal space could be directly measured by the diffraction patterns with transmission electron microscopy (TEM), the condition of atomic row matching would be easily identified in reciprocal space during TEM work, and could be applied to rationalize the experimental observations. Several examples in bothsmall and large misfit alloy systems are shown to apply the near tow matching method in both direct and reciprocal space. Furthermore, the row matching method is compared with other models, and there are some crucial aspects that need extra attention when being applied to prediction.


2014 ◽  
Vol 70 (a1) ◽  
pp. C375-C375
Author(s):  
Maciej Zubko ◽  
Joachim Kusz ◽  
Albert Prodan ◽  
Krystian Prusik ◽  
J. Craig Bennett

(NbSe4)3I is at room-temperature (RT) a semimetal, which changes at lower temperatures into a semiconductor [1]. The compound shows nonlinear transport properties with a second order phase transition at 274 K [2]. The symmetry of the RT (NbSe4)3I belongs to the P4/mnc space group and the structure is formed of NbSe4 antiprisms, stacked along the c axis. The Nb atoms are grouped into Nb2 segments and the Se-Se distances are correlated with the Nb chains. The I atoms occupy two types of channels; those running along the [00z] direction contain two I atoms connected to four Se atoms, while the channels along the [½½z] direction host two I atoms connected to eight Se atoms in a square anti-prismatic arrangement. At the (h,k,16n) planes a relatively strong diffuse scattering is present in the form of concentric rings. This scattering is explained by a similar model to the one recently suggested for (NbSe4)10/3I. The model is based on a mismatch between infinite NbSe4 chains, randomly shifted along the c direction. (NbSe4)3I was studied by means of X-ray and electron diffraction with beam precession (PED) [3]. PED patterns usually contain more Bragg peaks than the conventional selected area diffraction patterns, because the intensity of the diffracted beams is integrated over the selected volume of the reciprocal space. An additional advantage of using the beam precession technique is a reduction of the dynamical interactions. Electron diffraction patterns were recorded sequentially, while tilting the crystal around an arbitrary crystallographic axis. Such space tomography allows a three-dimensional inspection of the reciprocal space and a more precise investigation of the diffuse scattering from nano-areas.


2006 ◽  
Vol 39 (5) ◽  
pp. 752-756 ◽  
Author(s):  
Wen Bian ◽  
Hong Wang ◽  
Ian McCullough ◽  
Gerald Stubbs

Processing of fiber diffraction patterns is generally more difficult than for single-crystal patterns, and requires different algorithms and software. The programWCENhas been developed to determine experimental and specimen parameters and to convert diffraction data from detector to reciprocal space, and offers a variety of input and output formats, running under Mac OS X and Linux. The program is described and examples from oriented sols of filamentous plant viruses, illustrating different strategies for parameter determination and refinement, are given.


1970 ◽  
Vol 14 ◽  
pp. 11-28
Author(s):  
Dan McLachlan ◽  
Sylvia Chen

AbstractDespite the fact that the many researchers, who have worked on the problem of indexing powder diffraction patterns, have made several important advances in the field and have proven in theory at least that any pattern can eventually be indexed, the procedures are frequently so laborious as to drive the investigator to despair. Starting with the knowledge that convolution functions and particularly self-convolutions ﹛so well known to crystallographers as Patterson functions) have the power to find the distances between points in space, and knowing that reciprocal space is filled with repeating distances, the present authors have evolved a graphical system for carrying out the previously discovered procedures in an easy and rapid manner.


1963 ◽  
Vol 7 ◽  
pp. 94-106
Author(s):  
N. Cyril Schieltz

AbstractA brief and simple reciprocal space equation is derived for the X-ray camera setup, and the theoretical background necessary for graphical solutions is discussed. A typical graphical solution for powder patterns is carried out using the pattern of urea.


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