| Due to the unique structural and physical properties, one dimensional nano systems have the s significant scientific importance and wide potential applications. One dimensional nano systems include isolate nanowire, nanowire inside carbon nanotube (CNT), liquid inside CNT, etc. Our work investigates the effect of several physics parameters on the structural properties of those one dimensional nano systems. In particular, the first chapter of the thesis reviews the fundamental issue related to the thermodynamics and structure of one dimensional system. Following the method we used in this thesis:molecular dynamics (MD) simulation is discussed in chapter2. The third chapter studies the morphologies of liquid filled inside rigid CNT. The elasto-capillary phoneme of elastic deformation of CNT induced by filled liquid is presented in chapter4. The stable structures of confined nanowire and free standing nanowire are disscussed in chapter5and6respectively.The major findings of our work are reads:(1) Using molecular dynamics simulations, we studied the morphologies of Lennard-Jones liquid encapsulated in carbon nanotubes (CNTs) for a wide range of liquid-CNT interaction, system size and temperature. The morphology of liquid is found to be sensitive to the filling ratio of liquid (a ratio of liquid volume to the available volume of CNT pore and the liquid-CNT interaction. The’phase diagram’, namely by the morphologies versus the liquid-CNT interaction and the filling ratio, is obtained. In most cases, the liquid inside CNTs forms a thin liquid shell attached to a carbon wall when the filling ratio is small. With the increasing of the filling ratio, liquid tends to form droplet. As the filling ratio increases further, liquids form a cylinder with finite length. Finally, the whole inner space of CNT was filled with liquid when the filling ratio is large enough. Current studies could shed light on the adsorption and flow of liquid inside CNTs.(2) Both theoretical analysis and MD simulation are employed to investigate the deformation of elastic tube induced by filled liquid. We found that a CNT filled with separated liquid drops can be suddenly transformed from the circular shape into the ellipse shape associated with the coalescence of liquid drops. The structural deformation of the carbon nanotube has been regarded to be driven by the capillary forces. In order to explain such a structural collapse, we proposed a theoretical model. The theoretical model explained the collapse of the elastic tube very well and gave very consistent predictions with our molecular dynamics simulations.(3) Molecular dynamics simulations have been performed to investigate the structures of Lennard-Jones (LJ) nanowires encapsulated in CNTs. We found that the structures of nanowires in a small CNT only adopted multishell motif. While the structure of nanowires in a larger CNT tended to adopt various motifs. Among these structures, three structures were not reported previously. The phase boundaries among these structures were obtained regarding filling fractions, as well as the interaction between nanowires and CNTs.(4) By using MD method, we have studied the nanowires of four different metals (Ag, Mg, Ru, Ti). For each metal, we have compared the relative stability of four types of structures. The four structures include FCC and HCP crystal nanowire by Wulff construction. FCC five-fold multitwinned nanowire and HCP ten-fold multitwinned nanowire. Our results showed that, the stable structure of a certain metallic nanowire may change with the increase of cross section area. For most metals, either FCC or HCP, the FCC-based structure is most stable one as the radius of nanowires is small In a particular range of cross section area, ten-fold HCP multitwinned nanowire is the most stable structure for Ti. We also analyzed the stability of nanowire based on the excess energy. |
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