A statistical analysis of the breaking behavior of Ni nanowires is presented. Using molecular dynamic simulations, we have determined the time evolution of both the nanowire atomic structure and its minimum cross section (Sm(t)). Accumulating thousands of independent breaking events, Sm histograms are built and used to study the influence of the temperature, the crystalline stretching direction and the initial nanowire size. The proportion of monomers, dimers and more complex structures at the latest stages of the breaking process are calculated, finding important differences among results obtained for different nanowire orientations and sizes. Three main cases have been observed. (A) [111] stretching direction and large nanowire sizes: the wire evolves from more complex structures to monomers and dimers prior its rupture; well ordered structures is presented during the breaking process. (B) Large nanowires stretched along the [100] and [110] directions: the system mainly breaks from complex structures (low probability of finding monomers and dimers), having disordered regions during their breakage; at room temperature, a huge histogram peak around Sm=5 appears, showing the presence of long staggered pentagonal Ni wires with ...-5-1-5-... structure. (C) Initial wire size is small: strong size effects independently on the temperature and stretching direction. Finally, the local structure around monomers and dimmers do not depend on the stretching direction. These configurations differ from those usually chosen in static studies of conductance.
Comment on "Density Functional Simulation of a Breaking Nanowire"
在最近的一封信中，Nakamura等人[Phys. Rev. Lett. 82，1538（1999）]描述了断裂Na纳米接触的第一性原理计算。他们的系统由一个周期性的一维超晶胞阵列组成，每个超晶胞包含39个Na原子，最初形成一个长度为6个原子的直的晶体线。通过增加晶胞的长度来拉长系统。在每一步中，原子构型被放松到一个新的局部平衡，张力由总能量随伸长的变化来计算。除了在伸长的早期阶段从晶体到非晶结构的过渡处发生的力的不连续性之外，他们无法确定力与通过接触传递的电子模式的数量之间的任何简单的相关性。一个重要的问题是他们的模型是否现实，即，它是否可以与两个宏观金属片之间的单个纳米接触获得的实验结果进行比较。在这篇评论中，我们证明了这样一个小的单元格，相邻的接触之间的干扰效应是相同的大小，在一个单一的纳米接触的力振荡。
Microscopic analysis of the superconducting quantum critical point: Finite temperature crossovers in transport near a pair-breaking quantum phase transition
