Surface stress effects on the resonant properties of metal nanowires: The importance of finite deformation kinematics and the impact of the residual surface stress
Surface stress effects on the resonant properties of metal nanowires: The importance of finite deformation kinematics and the impact of the residual surface stress
复制标题
DOI：
10.1016/j.jmps.2008.08.003
复制
发表时间：
2008-11
影响因子：
5.3
通讯作者：
Harold S. Park;P. Klein
中科院分区：
文献类型：
--
作者：
Harold S. Park;P. Klein
我们利用最近发展的表面柯西-伯恩模型，该模型扩展了标准柯西-伯恩理论来解释表面原子配位不足引起的表面应力，研究了边界条件和表面应力对〈10 0〉金纳米线与{10 0}表面共振性质的耦合影响。这项工作有两个主要目的。首先，我们首次量化了由于表面应力引起的纳米线共振频率的变化，与相应的块体材料相比，根据使用的是固定/自由边界条件还是固定/固定边界条件，在有限变形框架内没有观察到表面效应。我们发现，虽然固定/固定纳米线的共振频率比相应的块体材料高，但由于表面应力引起的压缩应变，固定/自由纳米线的共振频率降低。此外，我们发现对于不同范围的纳米线几何形状，由于表面应力引起的两种边界条件的共振频率的变化是由纳米线长宽比表征的几何效应。在这两种边界条件下，本文的结果与已有的实验数据吻合得很好。这项工作的第二个主要目标是首次在非线性有限变形运动学的框架内量化表面应力的残余(应变无关)和表面弹性(应变相关)部分如何影响金属纳米线的共振频率。我们发现，如果考虑有限变形运动学，与应变无关的表面应力对纳米线的共振频率有很大的影响；然而，我们也发现，与应变相关的表面应力对纳米线的共振频率有显著的影响，其影响可以与依赖于边界条件的应变无关表面应力的影响相当，甚至比依赖于边界条件的应变无关表面应力的影响更大。
We utilize the recently developed surface Cauchy–Born model, which extends the standard Cauchy–Born theory to account for surface stresses due to undercoordinated surface atoms, to study the coupled influence of boundary conditions and surface stresses on the resonant properties of 〈100〉 gold nanowires with {100} surfaces. There are two major purposes to the present work. First, we quantify, for the first time, variations in the nanowire resonant frequencies due to surface stresses as compared to the corresponding bulk material which does not observe surface effects within a finite deformation framework depending on whether fixed/free or fixed/fixed boundary conditions are utilized. We find that while the resonant frequencies of fixed/fixed nanowires are elevated as compared to the corresponding bulk material, the resonant frequencies of fixed/free nanowires are reduced as a result of compressive strain caused by the surface stresses. Furthermore, we find that for a diverse range of nanowire geometries, the variation in resonant frequencies for both boundary conditions due to surface stresses is a geometric effect that is characterized by the nanowire aspect ratio. The present results are found to agree well with existing experimental data for both types of boundary conditions. The second major goal of this work is to quantify, for the first time, how both the residual (strain-independent) and surface elastic (strain-dependent) parts of the surface stress impact the resonant frequencies of metal nanowires within the framework of nonlinear, finite deformation kinematics. We find that if finite deformation kinematics are considered, the strain-independent surface stress substantially alters the resonant frequencies of the nanowires; however, we also find that the strain-dependent surface stress has a significant effect, one that can be comparable to or even larger than the effect of the strain-independent surface stress depending on the boundary condition, in shifting the resonant frequencies of the nanowires as compared to the bulk material.