why we are considering half of the atoms, actually isn't it one by fourth? One by fourth of each atom is inside that cell and also passing through the direction vector. Then why it is considered as half?
Sorry for the late reply. I was completely inactive. While calculating linear density we see how much length of the direction vector is occupied by an atom. Similarly, while calculating planar density we see how much area of the an atom is inside the plane under consideration. Hope, I have answered your question. Let me know if you still have doubt.
