讨论了纳米尺度下体系自由能的改变对扩散模型的影响.随着体系尺度的逐渐减小,扩散模型由Fick扩散定律转变为Cahn-Hilliard扩散方程和非均匀体系非线性动力学扩散模型,原子的扩散系数也随体系自由能的变化呈现出与局部原子浓度紧密相关的趋势.纳米尺度下体系自由能的变化是导致扩散模型改变的根本原因,体系非均匀性对自由能的贡献越大导致需采用非均匀体系非线性动力学扩散模型描述扩散.
Effect of free energy of system in nanoscale on the diffusion models is discussed. With the diffusion scale decreasing, the Ficks' laws change to the Cahn-Hilliard equation and the nonlinear kinetic discrete model, and the corresponding diffusion coefficients become to the strong concentration dependence due to the change of free energy of the system. It is found that the change of free energy of system is the main influencing factor for the change of diffusion models. The contribution of nonuniformity to the free energy of system makes the nonlinear kinetic diffusion model validity for description of diffusion in nanoscale.
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