Molecular Dynamics Study Of Water Flow Characteristics In Nanoscale Confined Space Of Molybdenum Disulfide

In recent years,molybdenum disulfide has attracted much attention by researchers because of its excellent physical and chemical properties,and it has a broad application prospect in semiconductor integrated circuits,flexible sensing and micro-nano electromechanical systems.In this thesis,the molecular dynamics method was used to study the water flow characteristics in molybdenum disulfide nanoconstrained channels,and the influence of the system charge,temperature and elastic strain on the water flow dynamic characteristics was discussed.The main work of the thesis was as follows:Basic properties of molybdenum disulfide,characteristics and applicability of different crystal structures(1T、2H、3R)were briefly introduced.The concept of nano-constrained space and the research background and current situation of molybdenum disulfide nanoconstrained channel fluid flow.The characteristics of fluid flow at nanometer scale in gap flow theory,penetration theory and transport theory were described respectively.From the theory of macroscopic fluid flow,the experimental research method of microfluidic flow was introduced,and the general law of microfluidic flow was summarized.The method of numerical simulation of microfluidics was analyzed and compared,and the molecular dynamics method suitable for this simulation was selected.The basic concept of molecular dynamics method,the equation of motion and the process of simulation were described in detail.the monolayer molybdenum disulfide model,water molecular model and water flow model in molybdenum disulfide nano-constrained channels were described in detail.And the conditions of ensemble,temperature control mode,force field and potential function in the simulation process were compared and analyzed.The variation of water molecular flow in molybdenum disulfide nanochannel under the influence of charge and temperature was investigated.the results show that the increase of the charge of molybdenum disulfide blocks the movement of water molecules,slows them down,and produces the phenomenon of ordered stratification.And the increase of system temperature will make the water molecules get more kinetic energy,so that the free diffusion motion of water molecules will accelerate,and the speed of movement will become faster.similarly,its diffusion coefficient and water molecular flow rate will also increase.on the contrary,the increase of temperature will reduce the peak value of the radial distribution function between oxygen atoms,which was due to the diffusion makes the molecular spacing become larger,which leads to the smaller probability of the occurrence of adjacent oxygen atoms in a certain distance range.The elastic strain engineering of water molecular flow in confined space was analyzed in detail,and the elastic strain engineering and the elastic strain model of molybdenum disulfide nano-limited space were described in detail.and by changing the elastic strain of the molybdenum disulfide nano-constrained channel,it was found that stretching will make the friction force on the surface of molybdenum disulfide become larger,which leads to the decrease of slip.Moreover,stretching makes the molecular spacing of molybdenum disulfide larger,the density distribution decreases,and the interaction force between solid and liquid weakens,so,resulting in a smaller density distribution of water molecules.This thesis studies the molecular dynamics of water flow characteristics in molybdenum disulfide nano-limited space,which provides theoretical basis and data support for the theory of fluid flow of water molecules at nanometer scale and its application in the production practice osmosis,filtration,memory alloys,etc.