Octahedral rotations in Ruddlesden-Popper layered perovskites under pressure from first principles

Octahedral rotations are ubiquitous in perovskite oxides and couple closely to their electronic and magnetic properties. Applying pressure to bulk perovskites tunes the octahedral rotation amplitudes, and in some cases changes the octahedral rotation pattern. While the pressure response of octahedral rotations in ABO₃ perovskites has been well studied, the impact of pressure on layered perovskites such as the n=2 Ruddlesden-Popper (RP) phase A₃B₂O₇ is much less explored. Here, we use density functional theory calculations to investigate the pressure response of several A₃B₂O₇ layered pervoskites. We find that these RPs have a distinct pressure response compared to ABO₃ materials. In particular, while the pressure response of ABO₃ perovskites often can be classified according to the charge state of the A- and B-site cations, we find that each of the A₃²⁺B₂⁴⁺O₇ RPs that we study exhibits a different response to pressure. Using a Landau expansion, we show how the interplay between different energetic contributions in RPs leads to this diverse set of responses to pressure. Our results offer insight into how to tune the structure and hence properties such as ferroelectricity in layered perovskites.