Critical anomaly and finite size scaling of the self-diffusion coefficient for Lennardben Jones fluids by non-equilibrium molecular dynamic simulation |
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Authors: | Ahmed Asad and Wu Jiang-Tao |
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Institution: | State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an 710049, China;State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an 710049, China |
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Abstract: | We use non-equilibrium molecular dynamics simulations to calculate the self-diffusion coefficient, D, of a Lennard-Jones fluid over a wide density and temperature range. The change in self-diffusion coefficient with temperature decreases by increasing density. For density ρ* = ρσ3 = 0.84 we observe a peak at the value of the self-diffusion coefficient and the critical temperature T* = kT/ε = 1.25. The value of the self-diffusion coefficient strongly depends on system size. The data of the self-diffusion coefficient are fitted to a simple analytic relation based on hydrodynamic arguments. This correction scales as N-α, where α is an adjustable parameter and N is the number of particles. It is observed that the values of α < 1 provide quite a good correction to the simulation data. The system size dependence is very strong for lower densities, but it is not as strong for higher densities. The self-diffusion coefficient calculated with non-equilibrium molecular dynamic simulations at different temperatures and densities is in good agreement with other calculations from the literature. |
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Keywords: | self-diffusion coefficient non-equilibrium molecular dynamic simulation Lennard-Jones fluid critical dynamics |
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