Classes of Rietveld parameters

Analytical expressions for the background (Eqs. 4.1 to 4.6), integrated intensity (Eqs. 2.65 to 2.108) and peak shape (Eqs. 2.49 to 2.63) have been considered earlier, and the minimum of the corresponding function defined by one of the relevant formulae (Eqs. 7.3 to 7.7) can be found by applying a non-linear least squares technique (see Eqs. 6.8 to 6.15). Thus, the following groups of independent least squares parameters are usually refined using the Rietveld method  

In this text, we are not specifically concerned with quantitative phase analyses of multiple phase mixtures, except for a single example considered in section 7.3.8, below. Interested reader is referred to an excellent overview given by R.J, Hill, Data collection strategies fitting the experiment to the need, in R.A. Young, Ed., The Rietveld method, Oxford University Press, Oxford, New York (1993). 

When more than two types of atoms occupy the same site, more than one variable per site may be adjusted. However, these cases are usually extremely difficult to refine sensibly. 

Parameter or group of parameters Linear in Eqs. 7.3 to 7.7 Stable Comment Sequence 

When the scale factor is far off, or when the model of the crystal structure is wrong or too far from reality, the refined scale factor may become incorrect. 

---