Study Of The Non-equilibrium Molecular Transport In Microscopic Channels

The phenomena of transport can be found easily in nature, its law can be understood and used by human beings in different fields of human activities such as food, neurons, biopolymers, medicament, soils with holes and the doping process of semiconductor etc.. We have made a great progress at the knowledgement of the laws in the history of scientific research, but our attentions focus mainly on the laws in the macro system. Conversely, the physical mechanism of transport in the micro system still remains unkown for us all the time.In this topic, we build one- to three-dimensional non-equilibrium molecular systems, and use molecular dynamics and Monte Carlo methods to simulate the process of molecular transport. Based on Fick’s law, we have investigated the relationship of the concentration, the mass flow and the diffusion coefficient. Moreover, we will verify that whether Fick’s law is still valid in non-equilibrium molecular systems. Our research will be helpful for researchers to understand and explore the microscopic mechanism of molecular transport in the future.The findings of our study include three parts:First, the factors, including the parameter ε of the Lennard-Jones potential, the atomic mass, the environmental temperature, the average concentration and the length of molecular transport, have a significant influence on the diffusion coefficient.Second, when the system is changed from one- to three-dimensional non-equilibrium molecular system with concentration gradient, the spatial dimension, the atomic mass, the environmental temperature, the average concentration and the length of molecular transport can affect the diffusion coefficient obviously, but the chirality of carbon nanotubes does not.Third, we have found two types of anomalous transport phenomena in asymmetric channel. One is the molecular pump which can be against concentration gradient. Its efficiency can be affected clearly by the angle and aperture of asymmetric channel, the attractive force of asymmetric channel, the environmental temperature, the average concentration and the atomic species. The other is the asymmetric transport of molecular sieve, the molecular behavior in sieve can be regulated by the environmental temperature, the atomic species and the aperture of asymmetric channel.