PDFgetX: a program for obtaining the atomic pair distribution function from X-ray powder diffraction data

For many materials with disorder, the local structure information is important in understanding their physical properties. However, the conventional crystal structure re®nement by the Rietveld method only allows the determination of the long-range average structure. The pair distribution function (PDF), which can be obtained from powder diffraction data, allows one to extract both local and average structural information (Petkov et al., 1999; Billinge & Thorpe, 1998). We present here a program, PDFgetX, for obtaining the PDF from Xray powder diffraction data. A similar program to process neutron powder diffraction data has already been published (Peterson et al., 2000).