Statistical analysis of the breaking processes of Ni nanowires

Abstract

We have performed a massive statistical analysis on the breaking behaviour of Ni nanowires using molecular dynamic simulations. Three stretching directions, five initial nanowire sizes and two temperatures have been studied. We have constructed minimum cross-section histograms and analysed for the first time the role played by monomers and dimers. The shape of such histograms and the absolute number of monomers and dimers strongly depend on the stretching direction and the initial size of the nanowire. In particular, the statistical behaviour of the breakage final stages of narrow nanowires strongly differs from the behaviour obtained for large nanowires. We have analysed the structure around monomers and dimers. Their most probable local configurations differ from those usually appearing in static electron transport calculations. Their non-local environments show disordered regions along the nanowire if the stretching direction is [100] or [110]. Additionally, we have found that, at room temperature, [100] and [110] stretching directions favour the appearance of non-crystalline staggered pentagonal structures. These pentagonal Ni nanowires are reported in this work for the first time. This set of results suggests that experimental Ni conducting histograms could show a strong dependence on the orientation and temperature.

Identification and characterization of icosahedral metallic nanowires

“…Depending on how the formation process occurs in every particular event, the ∆t 5 measure lacks to take into account the length of several pentagonal rings, and therefore underestimated the total icosahedral nanowire length. So the pentagonal nanowire length estimations of previous studies [10,11,12] reflected shorter lengths than the real ones. Only the direct measure of the length (applying the algorithm described in this paper or similar methods) can provide information about the formation of pentagonal chains, allowing the statistical study of the appearance of pentagonal nanowires.…”

“…We are interested in this study on the appearance and identification of icosahedral structures, so we have focussed on in nanowires stretched along the [100] direction due to their large probability to form pentagonal nanowires [10,11,12]. The number of atoms of the initial nanowire is 1029 (21 layers × 49 atoms per layer) and the temperatures used were T = 4, 160, 225, 300, 375, 465, 550, 690 and 865K (bulk Ni melting temperature T m = 1730K).…”

“…Different computational works during the last decade have showed the formation of staggered pentagonal configurations on breaking nanowires of different species [3,4,5,6,7,8,9,10,11,12]. The atomic sequence -1-5-1-5-presents a fivefold symmetry with respect the nanowire axis.…”

“…However, it is well known that the analysis of nanoscale processes requires the use of statistical approaches since there exists a broad bunch of breaking paths in the nanowire configuration space. Such statistical studies have been only addressed for Ni up to date [10,11,12]. It has been shown that [100] and [110] stretching direction favour the appearance of long pentagonal nanowires [10,11,12], and that there exists an optimal temperature at which the pentagonal nanowire yield is maximized [12].…”

Icosahedral Ni Nanowires Formed from Nanocontacts Breaking: Identification and Characterization by Molecular Dynamics

“…Pentagonal motives also appear in infinite Al and Pb nanowires obtained from MD simulated annealing methods [11]. More recently such structures have been reported for stretched Ni nanowires with different crystallographic orientations [10,12,13], and confirmed their stability by abinitio simulations [10,13]. These pentagonal structures are very stable, with lengths larger than 20Á and presenting a high plastic deformation under strain.…”