Enhanced polarization in strained BaTiO₃ from first principles

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The structure, polarization, and zone-center phonons of bulk tetragonal BaTiO₃ under compressive epitaxial stress are calculated using density functional theory within the local density approximation. The polarization, computed using the Berry-phase formalism, increases with increasing tetragonality and is found to be enhanced by nearly 70% for the largest compressive misfit strain considered (-2.28%). The results are expected to be useful for the analysis of coherent epitaxial BaTiO₃ thin films and heterostructures grown on perovskite substrates having a smaller lattice constant, such as SrTiO₃.