Perhaps I could make a small contribution to this discussion (I hope Alan will not mind too much). In the early 1970's I had my research group at the Cavendish Lab in Cambridge and I advertised for a postdoc to come and work on physical properties and structure of ferroelectric crystals (or something like that: my memory may not be precise). Alan at that time was working in Harwell and he applied for the job. I asked him to come and see me to discuss this and this was when I learnt about Rietveld. One should remember that prior to Rietveld (and Pawley) powder diffraction was a subject mainly used for identification of materials and had little general research impact. Anyway, I decided not to offer him the job, partly because I had another candidate who was experienced in physical property measurements of ferroelectrics, but also because I felt that it was in Alan's own interest to continue to concentrate on his Rietveld work. I think by this I did him a service!(true Alan?).
Anyway for a few years afterwards we collaborated on some Rietveld refinements, initially at Harwell and later at the ILL. Alan had taken Rietveld's original code and added some more coding to do anisotropic displacement parameters, and I think that our refinements of some perovskite structures included refinement of ADP's, which turned out to look reasonably meaningful. They seem to have stood the test of time. Going from memory, Alan it seems to me was the first person to latch onto the significance of Rietveld's program and was responsible for making it widely known. He deserves a lot of credit for this. My only other direct involvement in Rietveld (apart from just using it) was when I began working on synchrotron radiation. We collected powder data using a solid state energy dispersive detector. Despite its low resolution I was interested to see if we could apply the Rietveld process to the data. I had a young postdoc working with me and I asked him to have a go at writing some software to do this. It turned out that he was an awful programmer and it took a lot of time to get something working. In the end we succeeded (just!) and were able to get reasonable structural parameters from the data. Mike Glazer PLEASE NOTE : I SEND ALL FUTURE EMAILS TO ME AT mike.gla...@physics.ox.ac.uk
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