So, what is the purpose of this book? Herein, I want to present the important concepts needed for working with powder diffraction analysis, but with a modern and hands-on approach. This is work that requires computer software, so my goal is to present how and why these analyses are done, accompanied with theory when appropriate, but then present how to do that task using the widely-used and freely available crystallographic data analysis package GSAS-II. I think this is the most effective way to learn to become proficient in these analyses.
I am one of the two principal authors of GSAS-II and I am quite proud of the work done by my partner in its creation, Robert B. Von Dreele and I. We continue to work to make GSAS-II the best that we can. However, I do not want to make the assertion that GSAS-II is always the best tool for the job. There are a number of fine packages that include Rietveld analysis, including Topas, FullProf, JANA, Rietan and MAUD. Each offers some capability that GSAS-II does not. I am not sufficiently knowledgeable to introduce use of any of those packages here, so I will stick to GSAS-II. I do think that GSAS-II has the widest range of features; it is the most modern, started decades after many of the others; we work at making GSAS-II easily accessible to people getting started in the field; it runs on all types of computers in common use; and, you can’t beat the price (free).
However, Bob and I do not recommend the use of our previous software collaboration, GSAS/EXPGUI. This software has been superseded in every way by GSAS-II. There will be no future updates to GSAS or EXPGUI. As of today, GSAS/EXPGUI does run on Windows, but only with great difficulty on other modern platforms. GSAS was a marvel in its day. It had a very modern (non-graphical) user interface, at least in the 1980’s. GSAS was probably the first Rietveld program to have been written that did not contain any of Hugo’s original code. EXPGUI added a then-modern (1990’s) graphical user interface (GUI) to some of GSAS. Nonetheless, we can’t keep both packages alive, so it is time to say goodbye to GSAS/EXPGUI. Even the compilers/scripting packages needed for them are obsolete.