Hello Ahmed. It depends on the method you use. For Rietveld, you need quite a lot of parameters, i.e., both sample (structural) parameters and instrumental parameters. Regarding the first group, you have diadochy and defects, that make your sample (or its components) differ from the standards you need to use. But that's what Rietveld does: calculates this difference. More problematic is the way you prepare the sample: the more isogranular is the sample, the better results (i.e., less corrections need to be done by the computer). Also, there is preferred orientation, but this counts for quantitative analysis results rather than unit cell parameters. Regarding instrumental parameters, these are especially the Lorentz-polarization effect, zero of the detector shift (which is physically equal, more or less, to sample displacement - thus, these two parameters CANNOT be used together in any refinement).
In general, the better is the sample preparation, the better results you have. Good luck! Lukasz Kruszewski > Dear Rietvelders, > I am working on the precise measurement of > lattice parameters using X-ray diffraction data. Please let me know: > > 1. Precautions taken during the data recording using XRD. > > 2. How can we calculate lattice parameters precisely with in the 1x 10-5 > nm. > > 3. It is well known that XRD gives some % of errors, what is the reason > behind these errors. > > > > > Thankyou very much for your time. > > > -- > *Dr. Faheem Ahmed * > *Post Doc Fellow*- *Engineering Research Centre (ERC)* > *School of Nano and Advanced Materials Engineering, Building. No. 54, > Room- > 322 > Changwon National University, # 9 Sarim-dong, Changwon, Gyeongnam 641-773, > * > *Republic of Korea.* > > *Email:* faheem...@gmail.com > > *Ph No*. 0082-55-264-5431 (Office) > 0082-10-7263-6411 (Mobile) > -- Łukasz Kruszewski, Ph.D., adjunct Polish Academy of Sciences Institute of Geological Sciences X-Ray Diffraction Laboratory (coordinator) Twarda 51/55 str. 00-818 Warsaw Poland
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Please do NOT attach files to the whole list <alan.he...@neutronoptics.com> Send commands to <lists...@ill.fr> eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
