Very small shift in d-space: insanity check

Dear rietvelders I would like to consult with you as for the possibility to determine small shift in d-space in the order of 0.1pm in normal Bruker x-ray diffractometer with Bragg Brentano geometry

RE: Very small shift in d-space: insanity check

Hi Shay >From Bragg's equation we have: delta_theta = (delta_d/d) Tan(Th) Or, the amount a peak shifts is increases with 2Th but decreases with d-spacing. So at a d-spacing of 2 Angstroms say (200 pm) for a peak at 20 degrees 2Th say we would see a shift in 2Th of:

limitation sherrer formula

Dear Rietvelds The Scherrer formula is only applicable if the particle size is ~ 200 nm or less - it makes use of the line width due to the limited distance range ? This is true ? Wich paper are recomended to know why ? Best regards +++

RE: limitation sherrer formula

Nelson, There is no upper limit on particle size. The crystallite size limit depends only on your ability to measure a meaningful difference in line broadening between your sample and your instrument standard (e.g. LaB6, NIST SRM 660). A well aligned K-alpha1 machine can get you close to 1 micr

Re: limitation sherrer formula

Nelson, The easiest way to understand this is to insert values for the crystallite size and look at the FWHM it produces. The limit is the resolution of the FWHM measurement on your instrument, often based on step size. You can also determine the minimum FWHM you can differentiate and solve for th

RE: limitation sherrer formula

Nelson (and others) The Scherrer equation is a quick and easy method to get a feel for relative sizes for data from the same instrument and is still a useful tool in that regard. However, beware of relying on absolute values from the Scherrer equation in work to be submitted for peer review. De