Question

What can be concluded from two different values for the interplanar distance between planes of atoms in an X-Ray diffraction experiment?

Answer 1

The item you linked to is both an XRF and an XRD. Are you sure you have recieved a diffractogram problem

Answer 2

Explanation:

I analyzed an unknown Alkali Halide crystal using x-rays from a copper source. I need to find the d-spacing for this crystal, i.e. the interplanar distance between planes of atoms.

I found my Kα and Kβ peaks and used Bragg's Law to calculate the d-spacing. However, these values do not match. Is this an experimental error or could the non-matching values be correct somehow?

For Kα:

dhkl=

λ

(2sin(θ))

=

(1.54184Å )

(2sin((28.3°)/2))

=0.771Å

For Kβ:

dhkl=

λ

(2sin(θ))

=

(1.39222Å )

(2sin((25.7°)/2))

=2.488Å

My attempt: in both cases, I assumed that these were first order peaks. Could it be that the Kβ peak is actually a third order peak? If so, then n=3 and dhkl=2.313Å. This is reasonably close to the other value. But then what would that tell me about the crystal?