DoITPoMS

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Questions

Quick questions

You should be able to answer these questions without too much difficulty after studying this TLP. If not, then you should go through it again!

  1. In a simple X-ray scan, which of these affects the peak positions?

    Yes No a X-ray wavelength
    Yes No b Crystallite Size
    Yes No c Unit cell parameter
    Yes No d Atomic number

  2. Which of these is not involved in the diffraction of X-rays through a crystal?

    a Electron Scattering
    b Crystallographic planes
    c Nuclear interactions
    d Constructive interference

  3. What is the smallest d-spacing that can be measured for a given wavelength λ?

    a 0.5λ
    b λ
    c
    d no limit

Deeper questions

The following questions require some thought and reaching the answer may require you to think beyond the contents of this TLP.

  1. What sort of improvement in precision might you expect in cell parameter calculations when increasing 2θ?

  2. A crystal has a cubic unit cell of 4.2 Å. Using a wavelength of 1.54 Å at what angle (2 θ) would you expect to measure the (111) peak ?
    a. 10.6º
    b. 18.5º
    c. 43.0º
    d. 37º

  3. For a sample with a crystallite size of 100Å and using a wavelength of 1.54 Å estimate the peak breadth, in radians and degrees, of a peak at 60° 2θ.

  4. Given these experimental and reference data (A,B,C and D) which phases are:
    1. Definitely present
    2. Not observable (implies absent at any significant level)
    3. Unsure
    In each case give a reason for your answer and when unsure consider whether you could do something to clarify the situation.


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