Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

XRD peak position near 32 degree

  1. Oct 28, 2015 #1
    Why almost every crystal system has peak around 32 degree (2 theta) ?
  2. jcsd
  3. Oct 28, 2015 #2
    There are tens of thousand(s) (at least) known crystalline materials. How many of these have you checked to make the claim that "almost every crystal"?:smile:
    Of course, if you make the "around" wide enough it will true for any angle.

    Besides, the angle depends on the wavelength of the x-rays. Change your x-ray tube and the angles will change. So the 32 degree value cannot have any special meaning.
  4. Oct 28, 2015 #3


    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    I agree with nasu. This is an ambiguous, and frankly, meaningless claim.

    I did an XRD a couple of months ago on MgO. It looks almost like this:


    See any 32-degree peak anywhere?

    Last edited by a moderator: Apr 18, 2017
  5. Oct 28, 2015 #4

    I think it will be interesting to see how did you come to this impression. What systems did you study by XRD?
    Maybe they all have very similar structures.
  6. Oct 28, 2015 #5

    However, all ten thousand (s) of crystalline materials fall into 230 space groups only. out of that, many systems have peaks near 32 degrees. Very less number of systems have peak in the range of 20-30.
    I should not have used 'almost every'.
  7. Oct 29, 2015 #6
    Would you care to explain how you got this idea with the 32 degree angle? Otherwise there is no base for discussion.
    It's based on your own XRD measurements on some systems?

    The mention of 230 space group is not relevant. They can be all cubic crystals and still have all different peaks.
  8. Oct 29, 2015 #7


    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    .. or, as nasu has stated earlier, you can use the identical crystal and just change the x-ray wavelength, and the peak position changes!

    @madhusoodan, have you actually performed this XRD experiment yourself?

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook