Advanced Certificate in Powder Diffraction on the Web Chapter 24 School of Crystallography, Birkbeck College, University of London

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Aims & Objectives

The aim of this chapter is to provide you with some practical information on how to get started with Rietveld. The case study in the first chapter on Rietveld demonstrated the various steps in the refinement process, but from a non-practical (i.e. non-computational) perspective. This chapter aims to remedy the situation by providing some practical information for beginners. It is based solely around the use of Rietica as recommended for the course project, but some of the comments made in the text will be of a general nature when appropriate. (Rietica was chosen as it is fairly for beginners, but advanced users will want to try more advanced codes such as GSAS or Fullprof, both available via the CCP14 web site.)

More specific objectives are given below:

• You will learn how to simply view the data files supplied with the project using Rietica;
• You will learn how to setup new instrumental parameter files in Rietica;
• You will learn how to define manually the background count of your diffraction pattern;
• You will learn how to input the crystallographic model; and finally,
• You will learn how to start the whole refinement process.

After completing this chapter you should be able to:

• Refine the room-temperature structure of lead sulphate with Rietica by yourself (and you are strongly recommended to try this if you are a beginner at Rietveld refinement);
• Attempt the project.

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