The Mechanical Properties Of Single-walled Carbon Nanotubes Filled Gold Nanowires

Carbon nanotubes (CNTs), which can be regarded as coiled graphitic sheet with special structure, is found that they have excellent physical properties, such as high rigidity, outstanding electronic, mechanic properties. Over the past two decades, CNTs filled with nanoparticles and nanowires (NWs) have been intensively studied in experimental and theoretical works because the filling substances generally alter the host nanotubes' properties. Up to now, many elements have been successfully filled in the cavity of CNTs, for example fullerenes, metals (such as Cu,Pb,Fe) and many kinds of compounds. Compared with hollow CNTs, the filled CNTs generally present the high strength both in axial and radial directions, also have exotic optical and electronic properties different from hollow CNTs. It is well known that the mechanical properties of CNTs are important since they are the basis of other properties which can be utilized in many technologies. At present, the experiments under tensile, compression, bending, or torsion are usually adopted to discover the mechanical properties of CNTs, i.e. to calculate the relationship of stress and strain, furthermore to obtain the values of modulus.In present work, molecular dynamics (MD) simulations were used to study the buckling and post-buckling behavior of hollow and filled CNTs subjected to compression, bending and torsion load. In the simulations, the carbon-carbon interaction was described by Tersoff-Brenner potential, the carbon-gold interaction by Lennard-Jones potential, and the gold-gold interaction by Finnis-Sinclair potential.First of all, we investigated the buckling behavior of filled (8,8) and (10,10) armchair CNTs subjected to axial compression loading. It was found that the buckling force of filling CNTs are larger than that of hollow CNTs. As the strain increases, the potential energy of carbon atoms increases uniformly. When the strain reaches the critical value, the strain energy of CNT concentrates on the buckling position very quickly. Besides, the analysis of the encapsulated gold structure indicates that the gold nanowire forms 7-1 atom chains in the (8,8) tube, whereas, the gold nanowire in (10,10) tube is composed of 9-3 and 10-3 chains. During the deformation, the (8,8) tube buckled at the middle of CNTs, while the (10,10) tube buckled near the joints of 9-3 and 10-3. Furthermore, we traced the movement of gold atoms during the buckling. The bonds breaking and reforming among Au atoms were observed, which make the filled CNTs appear the metallic characteristicIn addition, the buckling behavior of filling (8,8) CNT under bending and torsion loading were studied. It is found that the critical bending and the torsion strength are 1.65 and 3.96 times of hollow CNT, respectively. The increment of the filled CNT strength for the two cases is much larger than that of axial compression.The highlight of this paper is that potential energy maps of CNTs are used to study the evolution of carbon wall under axial compression, bending and torsion loading. Using this method, it is convenient to observe the energy concentration, and to analyze the buckling and post-buckling mechanism of carbon nanotubes.