Modeling And Application Of Soft Matter By Multi-Particle Collision Dynamics

In this paper,we describe a algorithm of mesoscopic simulation for particle,namely multi-particle collision dynamics model(MPC),and using this method to study the dynamics of a nano-chain diffusing in porous media,and a series of configuration characteristics and power law were found;and establish a mesoscopic model of predator by signal molecules,and the properties of diffusion-capturing dynamics was studied,some interesting dynamical phenomena were found.In chapter 1,we firstly briefly discuss the numerical simulation technique.Then,a brief introduction of several common numerical simulation methods is written here,such as traditional methods based on N-S equation,Monte Carlo method,Molecular dynamics method,Lattice Boltzmann method,dissipative particle dynamics methods.In chapter 2,this article introduces the basic algorithm of MPC models,including the one-component systems and multi-component systems.Secondly,the algorithm has been proven that mass and momentum,energy and phase space volumes are conserved,and also shows that the algorithm does not satisfy the conservation of angular momentum.Then we briefly introduce the mixed multi-particle collision dynamics(MPC-MD)model.Finally we introduce the Verlet iterative algorithm.In chapter 3,a coarse-grained model is proposed to study the dynamics of a nano-chain diffusing in porous media by utilizing a hybrid method which combines MPC with molecular dynamics.The conformation,relaxation,and diffusion properties of a polymer chain are investigated by changing the density degree of the obstacle matrix.It is found that the average size of the chain is a non-monotonic function of the obstacle volume fraction(?).Dense environment may contribute to extend a linear chain,which can be characterized by bigger exponents in the corresponding power-law.The relaxation behavior of a stretched chain to a steady state shows dramatic crossover from exponent to power-law relaxation when the values of ? are increased.The dependence of diffusion coefficient on the chain size is also studied.We presented and discussed various kinds of scaling properties.The results can give additional insight into the density effect of porous media on polymer structure and dynamics.In chapter 4,a mesoscopic model is set up to study the predator-prey-like phenomenon between two chemical active objects by using a hybrid method which includes MPC and molecular dynamics.The decay coefficient,initial distance(d),the particle radius(R),energy parameters of pair particles are investigated,which effect capture time ct.The capture time increase as the decay rate.It is found that the values of capture time rely on their initial separation(d)as a power law(ct d??).The exponent depends on decay rate of signal molecules.The increase of particles size both leads to the decrease of the capture time,which is also shown by power law behavior.When increased energy parameters,the capture time can be reduced.In chapter 5,we summarize and discuss the MPC model.