The Study Of Collective Diffusion Properties Of Molecular Systems At Relativistic Velocity Motion Coordinates

Diffusion phenomenon is a common natural phenomenon,which has abundant applications in life and scientific research.Material transport is also a diffusion phenomenon,there have been many studies on its physical law in the static reference system,but the study of material transport in the high speed motion system is rare.Therefore,a nonequilibrium molecular system moving at relativistic velocity is constructed in this paper.The physical process of material transport at relativistic velocity motion coordinates is simulated by molecular dynamics and Monte Carlo method.The applica bility of Fick's law and the change of collective diffusion coefficient of non-equilibrium system moving at relativistic velocity are explored.Firstly,in the study of one-dimensional molecular transport,the relationship between temperature and diffusion coefficient of nonequilibrium molecular system is discussed.The results show that the relativistic velocity of the system has little effect on the temperature of the system,but the collective diffusion coefficient of the system decreases to zero as the speed of the system approaches the speed of light gradually.Considering the relativistic effect,the collective diffusion coefficient should be revised as (?).D'and D are the modified coefficient and the original coefficient,respectively.w is the relativistic velocity of the moving system,c is the speed of light.Secondly,a two-dimensional nonequilibrium molecular system at relativistic velocity motion coordinates is constructed.The results show that the diffusion law along the direction of relativistic velocity is different from that perpendicular to the direction of relativistic velocity because of the relativistic effect.Not only the Langevin equation used in the simulation is different,but also in the direction of X axis and Y axis,the shrinkage effect is different.All these lead to the difference between diffusion law and one-dimensional situation.Through numerical simulation,it is found that the revised formula of collective diffusion coefficient still satisfies D^'=g^-aD,in which?is Lorentz factor and?is revised coefficient.The velocity and the angle of the transport direction of the system have a significant influence on the collective diffusion coefficient.When the angle increases from 0 to 1,the correction coefficient decreases from 3 to 1.Finally,this paper considers the change of the rectification efficiency of the transport diffusion in a one-dimensional system moving at relativistic speed after adding an asymmetric external field.The main method is to add an external potential field consisting of cosine function to the previous one-dimensional transport study and observe the change of transport coefficient under the action of asymmetric external field.Under the action of the external field of the potential well,the influence of relativistic velocity is small,but under the action of the external field of the barrier,the relativistic velocity has a significant effect on the collective diffusion,and the rectification effect of the one-dimensional collective diffusion decreases gradually with the increase of the velocity of the system.In this paper,we attempt to extend the study of molecular transport diffusion from classical systems to relativistic systems.The results will help to understand the transport diffusion phenomena of particles in high-speed moving systems.Because the speed of material transport diffusion is closely related to the speed of human metabolism,this study will be helpful to explore the aging phenomenon of human body and organisms in high-speed flying vehicles or galaxies.