  In the development of first-principles high-throughput searches for materials
with desirable functional properties, there is a clear need for an efficient
method to determine the ground state and low-energy alternative structures of
superlattices. A method based on a simple strategy -- to generate starting
structures based on low-energy structures of the constituent compounds, which
are then optimized via structural relaxation calculations -- is proposed. This
"stacking method" is demonstrated on the 2:2 PbTiO$_3$/SrTiO$_3$ superlattice,
which has been the subject of recent experimental and theoretical interest.
Considerations relevant to wider use of the method are discussed.
