Advanced Certificate in Powder Diffraction
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Chapter 12 School of Crystallography, Birkbeck College, University of London |
Aims & Objectives
This is the first of two chapters on the subject of indexing and I am starting first with the concepts involved in unit-cell refinement. This may seem to be "putting the cart before the horse", but good data is essential if time is not to be wasted at the indexing stage of data analysis. Unit-cell refinements of standard materials are one of the best checks on instrument and sample alignment. This section introduces two web-interfaced programs that we will be making more use of later in the course. These are identified by the two icons below:
a program to generate hkl, d, and 2q values, and |
a program to refine unit-cell parameters. |
Make sure that you do the exercises that use these programs. The data have already been supplied in all of the examples, so in most cases you just submit the form without further ado.
Specific objectives include:
If any of the exercises give problems, please let us know. If the forms are incompletely downloaded you should get an error message; likewise, if the form contains bad data values. A reload can sometimes solve this problem. If all else fails, please contact us.
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