Ab initio study of metal/ferroelectric and insulator/ferroelectric heterostructures

We report first-principles calculations on the structural properties of SrRuO 3/BaTiO3
(metal/ferroelectric) and BaO/BaTiO3 (insulator/ferroelectric) heterostructures, both of them
paradigmatic systems for experimental measurements. Using a density-functional pseudopotential
plane-wave method, as implemented in the ABINIT package, we have studied the changes in the
interlayer spacing and the atomic rumpling. The substrates are explicitly considered in our simulations, so the lateral stress on the BaTiO3 thin films and mechanical boundary conditions are automatically taken into account. For the SrRuO3/BaTiO3 interface short-circuit boundary conditions are imposed. Results on free-standing BaTiO3 surfaces are also reported, showing good agreement with previous works. The ground state for all the structures studied here is paraelectric.