Number of atoms per unit cell: Primitive Cubic Unit Cell
Each cubic unit cell has 8 atoms on its corners. Therefore total number of atoms in one unit cell = 8 * 1 / 8 = 1 atom
Number of atoms per unit cell: Body Centred Cubic Unit Cell
In a body-centered cubic( bcc) unit cell, the atoms are present in the bodycenter besides the ones that are at its corners that wholly belongs to the unit cell in which it is present. Thus in a body-centered cubic( bcc) unit cell:
8 corners X 1 / 8 per corner atom = 8 * 1 / 8 = 1 atom 1 body center atom = 1 X 1 = 1 atom Total number of atoms per unit cell
= 2 atoms
Question: Niobium crystallises in body-centred cubic structure. If density is 8.55 g cm-3, calculate atomic radius of niobium using its atomic mass 93 u.
Answer: Density = 8.55 gcm-3 Consider length of the edge = a cm Number of atoms per unit cell, Z = 2