A supercell exists if the unit cell contains a subunit (or subcell) whose periodicity is smaller than that of the parent lattice (Nespolo, 2019). Therefore, the supercell consists of multiple translations of the subcell. However, the supercell is more complex than the simple translations of the subcell units because of offsets in the translations of the subcell, relaxation effects in the bonding within subcells, or more complex structural changes in one or more subcells. A crystal with a supercell structure will display extra diffraction peaks (or superlattice reflections) with respect to its subcell structure. In molecular simulations, a “supercell” is created by multiple repeats of a subcell equal to the periodicity of the unit cell. Calculations are then made on the supercell, which may deform the connectivity of the atoms within the subcell(s), resulting in a change of the subcell periodicity within the supercell. This supercell minimizes the effect of nearest neighbors in adjacent cells.
Cf., unit cell