-----Original Message----- From: May, Frank [mailto:frank.l....@umsl.edu] >My recollection is the Cagliotti function was adapted to the x-ray case when >we had low resolution x-ray instruments and slow (or no) computers. Now that >we have high resolution instruments and fast computers, why does this >inappropriate function continue to be used? There's probably a great deal of "it's always been done this way" in why its used, in addtion to a lack of education in when it should be used, as well as "Let's tick this box and see what happens"... :(
>On another note, the world is venturing into the infinitely small realm of >"nano-particles."... As the relative fraction of the "bulk" becomes smaller, >both the physical structure as well as the mathematics used to describe the >bulk suffer from termination-of-series effect, do they not? Does any of this >make sense? Any thoughts? This is talked about by Grey and Wilson*. They show that while you can refine diffraction data from nanosize titania particles, the numbers (cell params in this case...) that you get out might not represent what is actually there. Basically, the assumption that there is an infinite lattice breaks down. *Titanium vacancy defects in sol-gel prepared anatase Grey, I; Wilson, N JOURNAL OF SOLID STATE CHEMISTRY (0022-4596); Volume: 180; Issue: 2; Date: 2007; pg. 670-678 Cheers Matthew ________________ Matthew Rowles CSIRO Minerals Box 312 Clayton South, Victoria AUSTRALIA 3169 Ph: +61 3 9545 8892 Fax: +61 3 9562 8919 (site) Email: matthew.row...@csiro.au
