Development of a Charge-Implicit ReaxFF Potential for Hydrocarbon Systems

Molecular
dynamics (MD) simulations continue to make important
contributions to understanding chemical and physical processes. Concomitant
with the growth of MD simulations is the need to have interaction
potentials that both represent the chemistry of the system and are
computationally efficient. We propose a modification to the ReaxFF
potential for carbon and hydrogen that eliminates the time-consuming
charge equilibration, eliminates the acknowledged flaws of the electronegativity
equalization method, includes an expanded training set for condensed
phases, has a repulsive wall for simulations of energetic particle
bombardment, and is compatible with the LAMMPS code. This charge-implicit
ReaxFF potential is five times faster than the conventional ReaxFF
potential for a simulation of keV particle bombardment with a sample
size of over 800 000 atoms.

分子动力学（Molecular Dynamics，MD）模拟在阐释化学与物理过程的研究中始终发挥着关键作用。伴随MD模拟领域的快速发展，对相互作用势函数的需求日益提升——这类势函数既要能够精准表征体系的化学特性，又需具备较高的计算效率。我们提出了一种针对碳氢体系的ReaxFF势函数改进方案：该方案可省去耗时的电荷平衡步骤，修正了电负性均衡方法公认的固有缺陷，扩充了凝聚相体系的训练数据集，新增了适配高能粒子轰击模拟的排斥壁模型，且可兼容LAMMPS代码。针对原子数超过80万的keV级粒子轰击模拟场景，这款电荷隐式ReaxFF势函数的运行速度是传统ReaxFF势函数的5倍。