In X-ray diffraction (this is necessary reading for this node!) analysis of a crystalline solid, depending on the Miller indices of the material and the crystalline structure (BCC, FCC, SC), some expected reflections may not occur. This is due destructive interference in the refracted light.

In a simple cubic structure, no reflections will be absent. That is, if the material has any set of Miller indices, {h, k, l}, the planes therein represented will be reflected.

With a base centered cubic, however, reflections start to disappear. When the sum of the Miller indices is even, a reflection is seen. If however, the sum is odd, no reflection will be seen. For example {1,2,3} would show a reflection. {1, 0, 0} would not.

In a face centered cubic, reflections are seen as long as all of the Miller indices are odd, or all of them are even. If even and odd are mixed, no reflection would be seen. {2, 2, 2} would show up, whereas {2, 3, 1} would not.

If this seems confusing, I can't stress enough to read the hardlinks. It would be a waste of database space to duplicate that information here. The X-ray diffraction w/us are particularly relevant.

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