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[verstraete@pcpm.ucl.ac.be]

The term supercell should be defined in any solid-state textbook: the idea 
is that a crystal has a primitive unit cell with a minimal number of atoms 
(the cell). If you want to study a defect, or a surface, etc... in 
periodic boundary conditions, you need to take a cell big enough to 
simulate bulk material around your defect or under your surface. 
Therefore, you need more than one unit cell in your calculation; this is 
called a supercell. Basically a big cell which minimizes the effects of 
periodicity on localized defects.

Since the supercell is still a cell, the terms are often used 
interchangeably.

Matthieu



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Matthieu Verstraete               mailto:verstraete@pcpm.ucl.ac.be 
PCPM, Boltzmann, pl. Croix du Sud, 1        tel: +32 10 47 33 59
B-1348 Louvain-la-Neuve  Belgium            fax: +32 10 47 34 52