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In this paper, the effects of different orientations, size and temperature factors on the tensile deformation behavior of single-crystal body-centered cubic Fe nanowires were investigated using molecular dynamics simulations. The initial axial orientations of the iron nanowires are<001>, <110>,<111>,<102>, and <112>, and the deformation mechanisms were simulated at different temperatures (10-700K) and different size ranges (1.5 - 5nm). The results show that orientation, size and temperature significantly affect the tensile deformation behavior of single crystal body-centered cubic Fe nanowires. Molecular dynamics simulations show that <001> Fe nanowires with a diameter of 2 nm are deformed mainly through the mechanism of twinning under tensile loading at 300 K, and finally the tensile orientation is transformed to <110>. While at 700 K, the tensile deformation mode of <001 > Fe nanowires is dominated by slip mechanism. The deformation mechanisms of different initial orientations are very different at different temperatures and sizes, which leads to different mechanical properties of Fe nanowires. In this paper, we systematically investigate the transformation of the deformation mechanism of Fe nanowires under different orientations with the changes of size and temperature. [ABSTRACT FROM AUTHOR]

The dielectric properties of confined water have a significant impact on the energy storage efficiency of graphene supercapacitors. In this work, molecular dynamics simulation is taken to study the various effects on the dielectric constant of the confined water inside the graphene nanochannel. The results show that the structure of water-confined double electric layer in graphene nanochannels could be divided into three parts: gap layer, interface layer and bulk layer. The total dielectric constant decreases linearly with the channel height (h). It is attributed to the decrease of the thickness of the bulk layer. Moreover, the electrode voltage and the interaction strength parameter εCO between the graphene and the water molecule remarkably change the structure of Electrical Double Layers (EDLs) on the graphene surface. The increase of voltage greatly changes the polarization density distribution in the confined water and the degree of oscillation, resulting in a decrease of the overall dielectric constant. Similarly，the hydrophilic graphene surface (with high εCO) also significantly enhances the oscillation of confined water, leading to a decrease of the dielectric constant. [ABSTRACT FROM AUTHOR]

In order to effectively develop and utilize new energy, people urgently need high-performance super- capacitors to provide energy storage and conversion. Electric double layer structure plays a key role in supercapacitors. In this work, the molecular dynamics simulation was taken to an open graphene nanochannel (1-2 nm), and the double-layers structure of KCl solution inside the nanochannel was studied. Meanwhile, the similarities and differences of the double-layer structure under fixed charge simulation (Q) and constant potential simulation (U) were compared. The results show that the mirror image effect of the conducting graphene wall is considered in the constant potential simulation method, which makes the results more consistent with the practical materials. The mirror image effect can absorb extra ions. Thus it enhances the concentration of anion and cation in the pore, which may contribute to the improvement of electrode capacitance. Through the study of different channel heights, it is found that water molecules play a decisive role as dielectric materials in water-based supercapacitor. It can largely offset the change of electric double layer under different ions and different channel heights, resulting in a similar capacitance under different conditions. [ABSTRACT FROM AUTHOR]

Thedimension,structure and surface chemistry of nanochannels have great impact on the distribution structure and transport properties of the confined solutions. In this paper,a graphene prismatic nanochannel is proposed and investigated. This idealized channel is similar to the nanoporous structure of metal-organic framework material ( MOF), which has been widely studied recently,and has a completely different internal structure from the conventional carbon nanotubes. In this paper,the properties of KCl solution inside graphene prismatic nanochannel with different sizes are studied by molecular dynamics simulation,and then are compared with single-walled carbon nanotubes with the similar size. The results show that there are several high density areas inside the small channel ( ＜ 20 Å ),which is a tendency of crystallization. The results of this study will promote the structural design of MOF and the desire to achieve the nanochannel with high selectivity and high transport rate similar to biological ion channels. [ABSTRACT FROM AUTHOR]

The dielectric properties of confined water have a significant impact on the energy storage efficiency of graphene super capacitors. In this work, molecular dynamics simulation is taken to study the various effects on the dielectric constant of the confined water inside the graphene nanochannel. The results show that the structure of water-confined double electric layer in graphene nanochannels could be divided into three parts: gap layer, interface layer and bulk layer. The total dielectric constant decreases linearly with the channel height (h). It is attributed to the decrease of the thickness of the bulk layer. Moreover, the electrode voltage and the interaction strength parameter εCO between the graphene and the water molecule remarkably change the structure of Electrical Double Layers (EDLs) on the graphene surface. The increase of voltage greatly changes the polarization density distribution in the confined water and the degree of oscillation, resulting in a decrease of the overall dielectric constant. Similarly, the hydrophilic graphene surface(with high εCO) also significantly enhances the oscillation of confined water, leading to a decrease of the dielectric constant. [ABSTRACT FROM AUTHOR]