You can at least fit several layers of iron atoms into that gap, assuming they're part of the crystal lattice. So the surface does not have to be perfectly smoo

You can at least fit several layers of iron atoms into that gap, assuming they're part of the crystal lattice. So the surface does not have to be perfectly smooth. https://en.wikipedia.org/wiki/Atomic_radii_of_the_elements_(data_page)#Metallic_radius https://en.wikipedia.org/wiki/Atomic_radii_of_the_elements_(...