Ab initio design of charge-mismatched ferroelectric superlattices

We present a systematic approach to modeling the electrical and structural properties of charge-mismatched superlattices from first principles. Our strategy is based on bulk calculations of the parent compounds, which we perform as a function of in-plane strain and out-of-plane electric displacement field. The resulting two-dimensional phase diagrams allow us to accurately predict, without performing further calculations, the behavior of a layered heterostructure where the aforementioned building blocks are electrostatically and elastically coupled, with an arbitrary choice of the interface charge (originated from the polar discontinuity) and volume ratio. By using the [PbTiO3]_m/[BiFeO3]_n system as test case, we demonstrate that interface polarity has a dramatic impact on the ferroelectric behavior of the superlattice, leading to the stabilization of otherwise inaccessible bulk phases.

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