The variance as a measure of line broadening: corrections for truncation, curvature and instrumental effects

A correction for the unavoidable truncation of line profiles and an improved correction for the inherent curvature of the variance-range function are discussed. An analytical procedure for making the corrections is proposed and applied to theoretical and practical small-crystallite line profiles. An alternative procedure for obtaining the integrated intensity, and hence the integral breadth, and the variance (Fourier) apparent size is also presented.