The Kinetic Monte Carlo Simulation Of Diffusion Behavior Of Au Nanoparticle Defects

Nanoscience has become a hot spot in scientific research since the 1990s.Materials in the range of 1?100nm are its mainly research objects.Unlike ordinary objects in macro scale,nanomaterials have unique and abnormal physical and chemical properties,which attract the interest of many scientists.Noble metal nanoparticles is one of them.Because of its unique catalytic properties and excellent stability,noble metal nanoparticles have been widely researched,used in energy and chemical industry and biomedicine industry.The physical and chemical properties of noble metal nanoparticles are closely related to their size,morphology,surface defects,bulk defects,material structure,environmental temperature and pressure.Noble metal nanoparticles with more surface defects tend to have more surface-active sites and therefore have better catalytic performance.Tow-component or multi-component core-shell or alloystructured precious metals often show better catalytic activity and stability due to their synergistic effect between multiple metals.Many types of noble metal nanoparticles have been researched and prepared because of their unique physical and chemical properties.Defects are generally existed in materials.The existence of defects always has effects on the preparation of the material and the performance of the material after preparation.Therefore,to have knowledge of the dynamic behavior of defects is particularly important both for its preparation and application.In this paper,taking gold nanoparticle as an example,using Dynamic Monte Carlo method to study the dynamic behavior of bulk defects.Chapter one,firstly,I introduced the importance of materials.Secondly,I analyzed the factors affecting its unique physical and chemical properties of noble metal nanoparticles.Then,the discuss of defects of nanoparticles is presented.Chapter two,I gave a detailed introduction of numerical simulation in the field of computational materials,including(1)The First Principle.(2)Molecular Dynamic Simulation.(3)Monte Carlo Simulation.Finally,I introduced the Kinetic Monte Carlo(KMC)method and described the modeling process.Chapter three,I mainly analyzed the result of Kinetic Monte Carlo simulation and got several conclusions.For the dynamic tendency of bulk defects:(1)Bulk defects tend to migrate to the surface,and most defects will migrate from the bulk to the surface.(2)Bulk defects also tend to accumulate in the bulk,and a small number of defects will accumulate in the bulk to form small vesicles stably.(3)Small vesicles formed by body defects also tend to aggregate to form larger,more stable ones.Whereas small vesicles also have the tendency to migrate to the surface.(4)As for small gold nanoparticles,such as 10(?) in diameter,bulk defects will always migrate to the surface regardless of the defect concentration.(5)Gold nanoparticles with low defect concentration(1%,5%),the defect will migrate to the surface quickly and can not form stable vesicles in bulk.For the specific forms of defects migration:1.In bulk,defects migrate mainly through vesicles,alternatively,defects migrate with the vesicles.2.When the vesicles which formed by defects migrate to the near surface area,the defect will detach the vesicles and spread on their own.As the defects detach,the vesicles near the surface decreased in size and eventually disappeared.Chapter four,I summarized the work.