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Divergent electrostriction at ferroelectric phase transitions: example of strain-induced ferroelectiricty in KTaO3

We investigate the electrostrictive response across a ferroelectric phase transition from first-principles calculations and refute the prevailing view of constant electrostriction across the ferroelectric phase boundary. We take as a case study the epitaxial strain-induced transition from para- to feroelectricity of \ce{KTaO3}. We show that the magnitude of the electrostriction diverges with the permitivity at the transition, hence exhibiting giant responses through a calculation of both the M and Q electrostrictive tensors. We explain the origin of this giant electrostrictive response in \ce{KTaO3} using a microscopic decomposition of the electrostriction coefficients, and use this understanding to propose design rules for the development of future giant electrostrictors for electromechanical applications. Finally, we introduce a further means to calculate electrostriction, specific to ferroelectrics, and not yet utilised in the literature.