Paillard Charles, Xu Bin, Dkhil Brahim, Geneste Grégory, Bellaiche L
Laboratoire Structures, Propriétés et Modélisation des Solides, CentraleSupélec, CNRS UMR8580, Université Paris-Saclay, 92290 Châtenay-Malabry, France.
Physics Department, University of Arkansas, Fayetteville, Arkansas 72701, USA.
Phys Rev Lett. 2016 Jun 17;116(24):247401. doi: 10.1103/PhysRevLett.116.247401. Epub 2016 Jun 13.
An ab initio procedure allowing the computation of the deformation of ferroelectric-based materials under light is presented. This numerical scheme consists in structurally relaxing the system under the constraint of a fixed n_{e} concentration of electrons photoexcited into a specific conduction band edge state from a chosen valence band state, via the use of a constrained density functional theory method. The resulting change in lattice constant along a selected crystallographic direction is then calculated for a reasonable estimate of n_{e}. This method is applied to bulk multiferroic BiFeO_{3} and predicts a photostriction effect of the same order of magnitude than the ones recently observed. A strong dependence of photostrictive response on both the reached conduction state and the crystallographic direction (along which this effect is determined) is also revealed. Furthermore, analysis of the results demonstrates that the photostriction mechanism mostly originates from the screening of the spontaneous polarization by the photoexcited electrons in combination with the inverse piezoelectric effect.
本文提出了一种从头算方法，用于计算铁电基材料在光照下的形变。该数值方案通过使用约束密度泛函理论方法，在将电子从选定价带态光激发到特定导带边缘态的固定电子浓度(n_{e})的约束下，对系统进行结构弛豫。然后，沿选定晶向计算晶格常数的变化，以合理估计(n_{e})。该方法应用于块状多铁性材料BiFeO₃，预测的光致伸缩效应与最近观察到的效应量级相同。还揭示了光致伸缩响应强烈依赖于所达到的导带态和晶向（该效应沿此方向确定）。此外，结果分析表明，光致伸缩机制主要源于光激发电子对自发极化的屏蔽以及逆压电效应。
