Important properties of the unit cells are
– The type of atoms and their radii R.
– Cell dimensions (side a in cubic cells, side of base a and height c in HCP) in terms of R.
– n, number of atoms per unit cell. For an atom that is shared with m adjacent unit cells, we only count a fraction of the atom, 1/m.
– CN, the coordination number, which is the number of closest neighbors to which an atom is bonded.
– APF, the atomic packing factor, which is the fraction of the volume of the cell actually occupied by the hard spheres. APF = Sum of atomic volumes/Volume of cell.
