Molecular dynamics-smoothed molecular dynamics (MD-SMD) adaptive coupling method with seamless transition

摘要

Smoothed molecular dynamics ( SMD) method is a recently proposed efficient molecular simulation method by introducing one set of background mesh and mapping process into molecular dynamics ( MD) flow chart. SMD can sharply enlarge MD time step size while maintaining global accuracy. MD-SMD coupling method was proposed to improve the capability to describe local atom disorders. The coupling method is greatly improved in this paper in two essential aspects. Firstly, a transition scheme is proposed to avoid artificial wave reflection at the interface of MD and SMD regions. The new transition scheme has simple formulation and high efficiency, and the wave reflection can be well suppressed. Secondly, an adaptive scheme is proposed to automatically identify the regions requiring MD simulation. Two adaptive criteria, the centrosymmetry parameter criterion and the displacement criterion, are also proposed. It is found that both the two criteria can achieve good accuracy but the efficiency of the displacement criterion is much better. The coupling method does not demand reduction in mesh size near the interface, and a multiple time stepping scheme is adopted to ensure high efficiency. Numerical results including wave propagation, nano-indentation, and crack propagation validate the method and show nice accuracy. Copyright (C) 2016 John Wiley & Sons, Ltd.