The Research Of Physical Properties And Prediction Of Structure Of Low-dimensional Nanomaterials

Low-dimensional nanomaterials have unique morphology features and excellent physical and chemical properties, which have extensive practical value in physics,optoelectronics, catalysis and material preparation field. The research objects of low-dimensional nanomaterials including zero, one, and two-dimensional nanomaterials. Because of the unique optical, electrical and magnetic properties of low-dimensional nanomaterials make them become an important component of nano-photonics and have been used extensively in nano-photonics and nano-microelectronics field. With the rapid development of morden technologies and urgent demand of practical applications, it becomes particularly important to synthesise nanomaterials successfully experimentally. However, many experimental studies of nanomaterials are restricted by experimental equipments and conditions,leading to many physical properties of materials cannot be measured reliability by means of experiment. Therefore, it is essential to study the physical properties of nanomaterials by means of computational simulation technology.In this paper, the mechanical and thermal stability properties of low-dimensional nanomaterials are studied by using molecular dynamics simulation method. In my work, one-dimensinal Cd Se nanowires, Cu nanowires and zero-dimensional Ni nanoclusters are studied. We establish the initial structural models firstly and then study the physical properties and predict the possible structural transformation in consideration of different conditions. The research results will provide an important theoretical basis for experimental synthesis and properties study of low-dimensional nanomaterials. The main contents and results are presented as following:(a) We study the mechanical properties of zinc blend and wurtzite CdSe nanowiresand the thermal stability properties of wurtzite Cd Se nanowires also have been investigated. The research results show that:(1) The Young’s modulus and ultimate tensile strength of two kinds of Cd Se nanowires are decreasing with increasing the temperatures and sizes. During the stretching process of wurtzite Cd Se nanowires, we find two memorable phase transformations and a newly TAR-4 structure is observed for the first time.(2) The melting temperature of wurtzite Cd Se nanowires is strongly dependent on the size and growth orientation. It will increase as the size increased and the nanowires with [0001]-orientation have the highest melting point. What’s more, we find that the nanowires with [0001] and [10-10]-orientation exhibit surface premelting phenomena and the nanowires with [2-1-10]-orientation exhibit internal premelting behavior through investigation of the melting behavior of nanowires during heating.(b) The thermal properties and behavior of Ni nanoclusters with different sizes under different pressures are studied by using the constant pressure molecular dynamics method. The results show that the melting point of Ni nanoclusters will increase with increasing the pressure and size, and the Ni nanoclusters exhibit the surface premelting phenomena.(c) The torsional properties and behaviors of hollow Cu nanowires that coated and embedded with carbon nanotubes are studied by using the molecular dynamics method. We study the torsional critical angle of hollow Cu nanowires in consideration of temperature, torsional rate, size and investigate the torsional buckling behavior of hollow Cu nanowires after compositing with carbon nanotubes. The research results show that the critical torsional angle will do not change at high temperature and low torsional rate because of the support and protection of carbon nanotubes. However,the critical torsional angle of hollow Cu nanowires will increase with decreasing the size due to the surface effect of Cu nanowires.