Solution

ID: past-exam-of-the-condensed-matter-physics-course-of-the-university-of-oxford/2022/1/b/ii/solution

At each reflection, the argument of the atomic scattering factor is
Substitution into the given atomic scattering factor approximation gives
Thus the structure factors are and . The powder diffraction multiplicity is : choose which Miller index is zero in three ways and the signs of the other two in four ways. For , the eight sign choices give . With the specified instrumental and angular factors omitted, the integrated powder diffraction wave intensity is proportional to , so
It would be incorrect to use the same atomic scattering factors at the two different scattering vectors, or to omit the powder diffraction multiplicity.

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