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.
Identification of the Atomic Scale Structures of the Gold-Thiol Interfaces of Molecular Nanowires by Inelastic Tunneling Spectroscopy
我们从理论上研究了金-硫醇界面上的键合几何形状对桥接金电极的丙二硫醇（PDT）分子的非弹性隧穿光谱的影响，并表明非弹性隧穿光谱与理论相结合可以用来确定这些键合几何形状的实验。借助密度泛函理论，我们计算了由一个或两个PDT分子连接两个金纳米团簇组成的扩展分子的弛豫几何构型和振动模式。我们制定了一个微扰理论的非弹性隧穿分子桥接金属接触的弹性传输振幅，并使用此理论计算的非弹性隧穿光谱的金-PDT-金扩展分子。我们认为PDT分子与反式和gauche构象绑定到顶部，桥和空心键合位点的金簇。将我们的结果与Hihath等人的实验数据进行比较[Nano Lett. 8，1673（2008）]中，我们确定实验中最频繁实现的构象为与两个电极顶部结合的反式分子的构象。我们发现从42 meV的振动模式的46 meV的模式在实验中观察到的切换是由于过渡的反式分子从混合顶桥纯顶位键合的几何形状。我们的研究结果还表明，gauche分子构象和空心网站键并没有显着的实验非弹性隧穿谱的贡献。对于对PDT分子并联连接的金电极，我们发现总弹性电导接近两倍的单分子桥接的接触，具有类似的键合构象和小分裂的振动模式的能量的模式，是最敏感的分子电极键合几何形状。
Controlling the Spin-Wave Nonreciprocity of a Crescent-Shaped Nanowire via Curvature and Magnetic Field
Adam Mickiewicz University（亚当·密茨凯维奇大学）；Helmholtz--Zentrum Dresden--Rossendorf（德累斯顿-罗斯多夫亥姆霍兹中心）；V. G. Baryakhtar Institute of Magnetism of the NAS of Ukraine（乌克兰国家科学院 V.G. 巴里亚赫塔尔磁学研究所）
An {\it ab initio} study of the magnetic and electronic properties of Fe, Co, and Ni nanowires on Cu(001) surface
纳米尺度下的磁性由于其新颖的基础物理和令人兴奋的潜在应用，在过去的几十年里一直是一个非常活跃的研究领域。我们最近进行了一个{\it ab intio}研究所有3个$d$过渡金属（TM）独立原子链的结构，电子和磁性，发现Fe和Ni纳米线具有巨大的磁各向异性能（MAE），这表明这些纳米线将在高密度磁数据存储的应用。本文在广义梯度近似下，对Cu（001）表面Fe，Co和Ni线性原子链进行了密度泛函计算，研究了衬底对纳米线磁性的影响.我们发现Cu（001）表面上的Fe、Co和Ni线性链仍然具有稳定或亚稳的铁磁态。当考虑自旋-轨道耦合（SOC）时，由于3个$d$ TM链中SOC的弱性，自旋磁矩几乎保持不变，同时出现显著的轨道磁矩，并且也是方向依赖的。最后，我们发现Fe和Co的MAE仍然很大，即不太受Cu衬底的存在的影响。
Virtual Synthesis of Nanoscale Systems with Pre-Designed Properties: Fundamentals and Applications. Chapter 7. Nickel Oxide Quantum Dots and Polymer Nanowires
