Tutorial Functions

Using Functions

Files needed: alvo4-fn.inp

Learning Outcomes: Functions and advanced input files in topas.

This input file shows you how to use “functions” in the latest version of topas and essentially build a refinement from scratch including all the fundamental equations for scattering etc. The file uses restraints to fit hkl intensities for AlVO₄ and various functions to calculate structure factors etc. One to read and try and digest/understand. Will only work in topas v5 and later.

Can you see how you could combine the ideas in earlier tutorials of fitting individual peaks, using equations to predict peak positions, using fit_obj to describe the background and restraints to turn this input file into a full Rietveld fit? If you want to try this then the original powder data are in the test_examples directory.