Surface effects on the dual-mode vibration of <110> silver nanowires with different cross-sections

Dual-mode vibration of nanowires (NWs) has been reported experimentally through actuation of the NW at its resonance frequency, which is expected to open up a variety of new modalities for nanoelectromechanical systems that could operate in the nonlinear regime. In this work, we utilize large-scale molecular dynamics simulations to investigate the dual-mode vibration of 110 Ag NWs with triangular, rhombic and truncated rhombic cross-sections. By incorporating the generalized Young-Laplace equation into the Euler-Bernoulli beam theory, the influence of surface effects on the dual-mode vibration is studied. Due to the different lattice spacings in the principal axes of inertia of the {110} atomic layers, the NW is also modelled as a discrete system to reveal the influence from such a specific atomic arrangement. It is found that the 110 Ag NW will be under a dual-mode vibration if the actuation direction deviates from the two principal axes of inertia. The predictions of the two first mode natural frequencies by the classical beam model appear underestimated compared with the MD results, which are found to be enhanced by the discrete model. Particularly, the predictions by the beam theory with the contribution of surface effects are uniformly larger than the classical beam model, which exhibit better agreement with MD results for a larger cross-sectional size. However, for ultrathin NWs, current consideration of surface effects still experiences certain inaccuracy. In all, for all different cross-sections, the inclusion of surface effects is found to reduce the difference between the two first mode natural frequencies. This trend is observed to be consistent with MD results. This study provides a first comprehensive investigation on the dual-mode vibration of 110 oriented Ag NWs, which is supposed to benefit the applications of NWs that act as a resonating beam.