Enhancing the electromechanical response by engineering domain boundaries in multiferroics has become a highly active research field in recent years. The starting point is the discovery that ferroelastic twin walls are polar inside a non-polar matrix. The density of such twin walls is then greatly enhanced by forming complex twin patterns. Our computer simulations show that the interaction of nano-cavities with differently charged configurations with twin boundaries generates strong piezoelectricity in ferroelastic (non-ferroelectric) crystals. Cavity-induced domain patterns statistically break the inversion symmetry of a sample even when the cavities themselves obey inversion symmetry with relatively weak emerging piezoelectricity ($d$ ~ 10${}^{-3}$ pm/V). Stronger piezoelectricity occurs in non-centrosymmetric charged cavity arrangements with a coefficient of $d$ ~ 10${}^{-1}$ pm/V. Structurally, the electric field polarises and shifts the nano-cavities by the displacement of trapped surface charges. The related strain fields interact with the ferroelastic domains, which act as soft bridges between the nano-cavities. This leads to a significant deformation of the entire sample and hence to enhanced piezoelectricity. Our simulation results point to new directions for designing and enhancing electromechanical nano-devices based on ferroelastic templates even when the bulk material is structurally centrosymmetric.

中文翻译：

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具有纳米腔的孪生铁弹性体中增强的压电性

近年来，通过工程铁氧体边界来增强机电响应已成为一个非常活跃的研究领域。出发点是发现铁弹性双壁在非极性基体内是极性的。然后，通过形成复杂的孪生图案，极大地提高了这种孪生壁的密度。我们的计算机模拟结果表明，具有双边界的带不同电荷配置的纳米腔相互作用在铁弹性（非铁电）晶体中产生强压电性。即使空腔本身在相对较弱的新兴压电性下服从反演对称性的情况下，由空腔引起的畴模式也从统计学上打破了样品的反演对称性（$d$ 〜10${}^{-3}$pm / V）。在非中心对称带电腔布置中会产生更强的压电性，其系数为$d$ 〜10${}^{-\mathrm{1个}}$pm / V。在结构上，电场通过捕获的表面电荷的位移极化并移动纳米腔。相关的应变场与铁弹性域相互作用，该铁弹性域充当纳米腔之间的软桥。这导致整个样品的显着变形，因此导致压电性增强。我们的仿真结果为基于铁弹性模板的机电纳米器件的设计和增强提供了新的方向，即使主体材料在结构上是中心对称的。