  Based on the molecular dynamics (MD) simulation and the classical
Euler-Bernoulli beam theory, a fundamental study of the vibrational performance
of the Ag nanowire (NW) is carried out. A comprehensive analysis of the quality
(Q)-factor, natural frequency, beat vibration, as well as high vibration mode
is presented. Two excitation approaches, i.e., velocity excitation and
displacement excitation, have been successfully implemented to achieve the
vibration of NWs. Upon these two kinds of excitations, consistent results are
obtained, i.e., the increase of the initial excitation amplitude will lead to a
decrease to the Q-factor, and moderate plastic deformation could increase the
first natural frequency. Meanwhile, the beat vibration driven by a single
relative large excitation or two uniform excitations in both two lateral
directions is observed. It is concluded that the nonlinear changing trend of
external energy magnitude does not necessary mean a non-constant Q-factor. In
particular, the first order natural frequency of the Ag NW is observed to
decrease with the increase of temperature. Furthermore, comparing with the
predictions by Euler-Bernoulli beam theory, the MD simulation provides a larger
and smaller first vibration frequency for the clamped-clamped and clamped-free
thin Ag NWs, respectively. Additionally, for thin NWs, the first order natural
frequency exhibits a parabolic relationship with the excitation magnitudes. The
frequencies of the higher vibration modes tend to be low in comparison to
Euler-Bernoulli beam theory predictions. A combined initial excitation is
proposed which is capable to drive the NW under a multi-modes vibration and
arrows the coexistence of all the following low vibration modes. This work
sheds lights on the better understanding of the mechanical properties of NWs,
and benefits the increasing utilities of NWs in diverse nano-electronic
devices.
