training for advanced research


Glossary terms about Diffraction

The scattering of waves by objects they interact with. Diffraction effects are most powerful when the diffraction objects are regularly spaced, and the spacing is similar in size to the incident wavelenght.

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33 pages mention Diffraction

Additional material
Analysis of data
Qualitative powder diffraction involves the identification of a phase or phases in a specimen by comparison with single-phase X-ray powder diffraction patterns compiled in a database called the Powder diffraction File (PDF-2). 
Applications of XRD
X-ray diffraction (XRD) can be used to unambiguously characterize the composition of pharmaceuticals. 
Background information
X-ray diffraction is a tool for the investigation of the structure of matter. 
Many techniques, including powder x-ray diffraction, require the use of monochromatic radiation (single wavelength x-rays). 
Crystal groups
Visual representations of the systems can be found here, in a page of the TEM module. 
Although he did not know why this was true (x-rays had not yet been discovered, much less x-ray diffraction invented), we now know that this is so because studies of the atomic structure of any mineral proves that the structure remains within a close set of given limits or geometric relationships. 
Entry slit at low angles
Interactive simulation of x-ray diffraction
Exit slit
Interactive simulation of x-ray diffraction
How to process XRD files in EVA
Interesting facts
Powder diffraction is a standard analytical technique not only in concrete industry but also in pharmaceutical chemistry. 
Powder x-ray diffraction (XRD) uses x-rays to investigate and quantify the crystalline nature of materials by measuring the diffraction of x-rays from the planes of atoms within the material. 
Nobel prizes for research with X-Rays
von Laue in Physics for x-ray diffraction from crystals. 
The output from an X-ray diffraction experiment is usually presented as a diffractogram in which the intensity of diffracted x-rays is shown as a function of the scanning angle 2θ. 
Peak intensities
While crystal planes and lattices are helpful to understand the laws of diffraction, they are not what X-rays “see”. 
Powder diffraction
Now that the effect of diffraction on a crysalline sample has been described, it is time to discuss the core concept of this module: how diffraction of a polycrystalline sample (usually a powder) works. 
Powder diffractograms
In X-ray diffraction, the X-ray detector moves along a 2θ-circle with the sample in the centre of the circle. 
Powder diffractometer
However, a major part of information is lost: in single crystal diffractions the diffraction peaks occupy a three dimensional space which is called the reciprocal space. 
Primary optics
The primary optics controls the beam produced by the X-ray source, and manipulates it into forms more useful for diffraction experiments. 
There are a number of safety guidelines and factors to consider when using the equipment for X-ray diffraction
Sample preparation
Proper sample preparation is one of the most important requirements in the analysis of powder samples by X-ray diffraction
Secondary optics
Single crystal diffractometer
Using these axes as a coordinate system, the diffraction peaks themselves describe a lattice in three-dimensional space which corresponds to the crystal lattice. 
The source produces the X-rays used for analysing samples with X-ray diffraction
Sources - iron poor samples
Interactive simulation of x-ray diffraction
Sources - iron rich samples
Interactive simulation of x-ray diffraction
Step-by-step instructions to use the Bruker D8 advanced research XRD
Tailor this module
The Ewald sphere
A most useful means to understand the occurrence of diffraction spots is the Ewald sphere. 
X-ray diffraction in practice
Safety in X-Ray diffraction  
X-ray structure interaction
So are the patterns, which cause diffraction effects with X-rays. 
After learning that Paul Ewald's optical theories had approximated the distance between atoms in a crystal by the same length, Laue postulated that X-rays would diffract, by analogy to the diffraction of light from small periodic scratches drawn on a solid surface (an optical diffraction grating).