Due to the electromechanical coupling effect, composition-graded InGaN nanowires (NWs) have promising potential application in piezotronics. However, as an inhomogeneous system at the nanoscale, the electromechanical response of InGaN NWs can be affected by some small-scale effects, e.g. the flexoelectric effect, which is almost unexplored. In this paper, the piezoelectric and elastic properties of composition-graded InGaN NWs are investigated by using molecular dynamics (MD) simulations, in which a power-law formula is introduced to describe the continuously varied composition in graded InGaN NWs. MD results show that the diameter, Young’s modulus and piezoelectric coefficient of graded InGaN NWs are dependent on the position of NWs. Moreover, the distribution of these structural and material parameters can be efficiently modified by changing the power-law exponent. The position-dependent diameter and Young’s modulus can be well described by Vegard’s law. However, as for the piezoelectric coefficient, a big discrepancy is observed between the results extracted from MD simulations and Vegard’s law. This discrepancy is attributed to the enhanced piezoelectricity in graded InGaN NWs induced by the flexoelectric effect. The flexoelectric effect is found to originate from the non-uniform strain in graded InGaN NWs majorly induced by the varied Young’s modulus along the NW axis, which becomes more significant as the length of NWs decreases. This work tries to present a comprehensive understanding of the electromechanical coupling of InGaN NWs, which can provide guidance for the design of graded InGaN NWs-based piezotronic nanodevices.

由于机电耦合效应，成分梯度 InGaN 纳米线 (NW) 在压电电子学中具有广阔的应用前景。然而，作为纳米级的非均匀系统，InGaN NWs 的机电响应会受到一些小规模效应的影响，例如几乎未开发的挠曲电效应。在本文中，通过使用分子动力学 (MD) 模拟研究了成分渐变 InGaN NW 的压电和弹性特性，其中引入了幂律公式来描述渐变 InGaN NW 中连续变化的成分。MD 结果表明渐变 InGaN NW 的直径、杨氏模量和压电系数取决于 NW 的位置。而且，通过改变幂律指数可以有效地修改这些结构和材料参数的分布。位置相关的直径和杨氏模量可以通过 Vegard 定律很好地描述。然而，对于压电系数，从 MD 模拟中提取的结果与 Vegard 定律之间存在很大差异。这种差异归因于由挠曲电效应引起的渐变 InGaN NW 中增强的压电性。发现挠曲电效应源于梯度 InGaN NW 中的非均匀应变，主要由沿 NW 轴变化的杨氏模量引起，随着 NW 长度的减小，这种应变变得更加显着。这项工作试图全面了解 InGaN NW 的机电耦合，