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William Lawrence Bragg proposed a model where the incoming X-rays are scattered specularly (mirror-like) from each plane; from that assumption, X-rays scattered from adjacent planes will combine constructively (constructive interference) when the angle θ between the plane and the X-ray results in a path-length difference that is an integer ...
X-ray diffraction computed tomography is an experimental technique that combines X-ray diffraction with the computed tomography data acquisition approach. X-ray diffraction (XRD) computed tomography (CT) was first introduced in 1987 by Harding et al. [1] using a laboratory diffractometer and a monochromatic X-ray pencil beam.
MM XRD: Free open-source: Java 3D applet or standalone program: Ovito: MM XRD EM MD: Free open-source: Python [13] [14] PyMOL: MM XRD SMI EM: Open-source [15] Python [16] [self-published source?] According to the author, almost 1/4 of all published images of 3D protein structures in the scientific literature were made via PyMOL. [citation ...
As regards weighting, one can either weight all of the measured ages equally, or weight them by the proportion of the sample that they represent. For example, if two thirds of the sample was used for the first measurement and one third for the second and final measurement, then one might weight the first measurement twice that of the second.
To see where the Scherrer equation comes from, it is useful to consider the simplest possible example: a set of N planes separated by the distance, a. The derivation for this simple, effectively one-dimensional case, is straightforward. First, the structure factor for this case is derived, and then an expression for the peak widths is determined.
A powder X-ray diffractometer in motion. X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract in specific directions.
calculation of () Radial distribution function for the Lennard-Jones model fluid at =, =.. In statistical mechanics, the radial distribution function, (or pair correlation function) () in a system of particles (atoms, molecules, colloids, etc.), describes how density varies as a function of distance from a reference particle.
Rietveld refinement is a technique described by Hugo Rietveld for use in the characterisation of crystalline materials. The neutron and X-ray diffraction of powder samples results in a pattern characterised by reflections (peaks in intensity) at certain positions.