Understanding formation mechanism of ZnO diatomic chain and multi-shell structure using physical mechanics: Molecular dynamics and first-principle simulations?

Abstract

In this paper, the possibility of the monatomic chain (MC) formation for ZnO material was studied by molecular dynamics (MD) simulation. The process of MC formation and the effects of temperature, strain rate and size were studied extensively. The tensile process can be divided to be five stages and the ZnO diatomic chain (DC) can be found. The MD results show that most atoms in MC came from the original surface of ZnO nanowires (NWs). Temperature and strain rate are two important factors affecting the process, and both high temperature and low strain rate in a certain range would be beneficial to the formation of DC. Moreover, the effects of strain rate and temperature could attribute to the Arrhenius model and the energy release mechanism. Furthermore, multi-shell structure was found for the samples under tensile strain and the layer-layer distance was about 3 Å. Our studies based on density functional theory showed that the most stable structure of ZnO DC was confirmed to be linear, and the I-V curve was also got using ATK. Figure 1, which illustrates a systematic trend of the increase in experimental yield strength of a Au nanostructure as the size is reduced towards the atomistic scale. The first direct observation of gold MC was found in 1998 and the conductance was also studied [4]. MC has many unique properties such as the smallest electrical wire and ultimate surface-to-volume ratio. Thus MC has potential applications in electronic devices and high-performance gas-sensing devices. Moreover, MC is an ideal prototype of a nanowire (NW) for extensibility and mechanical strength study as no processes of bond unfolding or atom glide dislocating are involved in the deformation [5].The atomic chain may possibly transport current with high density and be applied to molecular devices. Therefore, various materials such as Pt and Ni were studied experimentally and theoretically. From both experiments and calculation, NWs show quantized conductance units of 2e 2 =h, and single chains of gold atoms were confirmed to have one unit of conductance [6,7]. Many techniques such as pulling atoms with a scanning tunneling microscope (STM), separating two metals with a mechanically controllable breaking

Formation of pentagonal atomic chains in BCC Fe nanowires

“…Each tube consists of helical atom rows coiled round the wire axis. The structures such as linear atomic chain (monatomic, diatomic), pentagonal, twoshell, three-shell and helical multi-shell structures have also been predicted theoretically in ultra thin Al and Pb metallic nanowires 8 and also in ZnO and Si semiconductor nanowires using molecular dynamics simulations 9,10 . In Al and Pb metallic nanowires, it has been postulated that the competition between optimal internal packing and minimal surface energy is the main driving force behind these morphological structures at small size 8 .…”

“…This is due to the inherent timescale limitations from MD simulations. Here, it must be noted that the strain rate also influences the formation of linear and pentagonal atomic chains 9,12 . For each size and temperature, five independent simulations have been carried out to make statistically meaningful conclusions.…”

Negative differential resistance behavior of silicon monatomic chain encapsulated in carbon nanotubes

“…It should be noted that the similar monatomic chains were reported only in a few experiments [16] or modeled in simulations [17,18]. However, in recent years, research on the electron transport properties of molecular devices has attracted increasing attention.…”

How to identify dislocations in molecular dynamics simulations?

“…With the availability of more accurate simulation models and more powerful computing resources, increasingly complex problems in materials science can be addressed and studied at the atomic level [12]. Thus, atomic simulation has been used more extensively to investigate the mechanical properties of crystalline materials [13][14][15][16][17][18].…”