FVM-MD耦合算法中非周期性边界条件的研究

Investigation of Non-Periodic Boundary Condition Used in FVM-MD Coupling Simulations

本文研究了广泛应用于耦合算法中的非周期性边界条件(NPBC),获得了耦合算法中粒子区边界附近原子所受边界力与边界处局部密度和温度的关系。基于此,本文拟合得到了边界力与局部密度和温度的关系式,与平衡态分子动力学模拟结果的对比验证了拟合公式的可靠性。最后本文将边界力的拟合公式应用到耦合算法中求解Poiseuille流动,结果表明粒子区边界附近的密度振荡大大减小,且速度和温度分布曲线能很好地与纯MD方法结果吻合。

This paper presents an investigation of the non-periodic boundary condition （NPBC） which is often used in multiscale molecular-continuum simulations. The relationship between the boundary force exerted by the atoms outside the atomistic domain and the density and temperature at the boundary is studied. Fitting formulas of the boundary force as function of the fluid state has been proposed based on the relationship. The accuracy of fitting formulas is verified by the equilibrium MD simulation results. Poiseuille flow is then simulated using the proposed fitting formulas. The elimination of density oscillation near the boundary of atomistic region further confirm the correctness of our fitting formulas.