Correction for the satellite group in the variance method of profile analysis

Three methods are described of eliminating the influence of the satellite group in the variance method of X-ray line profile analysis. The first is to interpolate the line profile under the satellite group: however, the satellite group must be reasonably well distinguished from the α₁ tail and from the background. The second method is to correct the experimental variance-range curve by a graphical construction: this assumes that the satellite lines and the broadening function are Cauchy in form. The third method is to compute the necessary corrections to the slope and intercept of the linear variance-range function by using model spectral distributions with and without the satellite group. The first two methods are applied to profiles from powders of iron and iron alloys studied with iron radiation, the third method uses an analytical model of the spectral distribution of the iron Kα multiplet. The corrections given by these methods to be made to the slope and the intercept of the variance-range function are nearly constant for all but the smallest amounts of particle-size broadening. It is also shown that particle sizes determined either from slope or intercept of the variance will be underestimated if correction is not made for the satellite group.