The resulting characteristic values

The processing of diffraction diagrams makes it possible to extract three essential values from each peak  

Precisely determining one or another of these values requires taking precautions specific to the machine used. We will see in Chapter 4 that, depending on the information sought, one or several of these parameters have to be determined. The experimental conditions associated with the production of diffraction patterns are directly related to the information we wish to extract. In this section, we will give more details on the acquisition conditions and on the adequate processing methods for measuring each of these values. 

Peak positions, which correspond to the values of the difiiaction angles, are the most commonly used information in the interpretation of diffraction patterns, since they make it possible to determine the material s specific interplanar distances with the use of Bragg s law (nA, = 2d sin 0). 

Generally speaking, it can be shown that the accuracy of a diffractions peak s position increases with the diffraction angle. In fact, Bragg s law is written nX = 2d sin 0 and therefore  

This means that a given error in the measurement of 0 will lead to an error on d that decreases when 0 gets closer to 90°. Likewise, if we consider a set distance d, but a wavelength that can vary slightly, we get  

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