XRD-Shorter distance between planes than actual radius of atoms/or cell parameter I'm solving problems related to X-ray diffraction, and I get these results which apparently are correct. My question may be dumb, but I just can't see how the interplanar distance might be shorter than the atoms radius. 

What's up with this?

I think it might make sense that its shorter than the cells parameter, but it's not immediately obvious to me, so if someone could prove it to me, i'd be quite glad.

Edit: 

For example:

The atomic radius of chromium is 124pm. THe distance between (310) planes is .0912nm. 
See problem 6
Does this help?



The distance between planes will be less than the distance between atoms in many cases because the atoms don't have to stack directly on top of one another in each plane.