Materials with the perovskite structure exhibit a nearly
unparalleled range of electronic, magnetic, and transport properties:
by simply varying chemical composition, perovskites may possess high
dielectric constants, ferroelectricity, ferromagnetism, or
superconductivity. Their common structural template has, in part,
facilitated the recent development of techniques for their
layer-by-layer epitaxial growth. Given these techniques, myriad
multifunctional heterosystems, where structural, electronic, and
magnetic phenomena may vary on the nanoscale, become possible; a
pivotal remaining question concerns what should be grown. In
this talk, I demonstrate the ways in which first-principles
density-functional calculations can be used to design and assess the
properties of epitaxially-grown perovskite oxides through two
examples: paraelectric/ferroelectric superlattices, such as
BaTiO3/SrTiO3; and weakly-ferromagnetic ferroelectric BiFeO3 ultrathin
films. The respective roles of composition, interfacial structure and
chemistry, internal fields arising from non-bulk electrical boundary
conditions, and the considerable strains associated with coherent
epitaxy are elucidated through a quantitative, atomic-scale analysis.
Recent experiments, and implications for future work, are
discussed.