Xray Diffraction 4.5

Physics Q&A
1

Hi,

In the answers for the question “Calculate the lattice constant of the conventional chromium bcc unit cell. Use that the X-ray diffraction experiment was carried out using Cu K-\alpha”
it states d_{200} = 0.145nm and then it further concludes that a must then be 0.29nm. I’m lost on how we immediately jump to that conclusion based on that value for d as I can’t find any distinct way to compute that. My best guess is using the formula we derived at 2.2 which was to use d = n*\frac{a_1}{h} and since a_1 has a length of a and h a value of 2 here, then a = 2*d but I was wondering if that was correct?

2

Hi Karel,
I believe in this exercise you have all the ingredients to make use of Bragg’s law! That connects the wavelength of the source you’re using, \lambda, with the diffraction angle, \theta, and the distance between successive Miller planes d_{hkl}.

Once you figure that out, you need to find a connection between d_{hkl} and the lattice constant.

Good luck, and come back if you need more help :grin: