Systematic evaluation and refinement of existing all-atom force fields for the simulation of liquid acetonitrile.

The reliability of a molecular dynamics (MD) simulation study mainly depends on the accuracy of the applied force field. Unlike the ability of some potential models for reasonably predicting the thermodynamic properties of acetonitrile (ACN), simulated dynamical properties such as self-diffusion are generally underestimated compared to experimental values. The present work focuses on the evaluation and refinement of several available all-atom force fields for ACN and proposes a refined flexible six-site potential model. The main modification is related to the reduction of intermolecular LJ parameters (σ and ɛ) for hydrogen atoms, especially ɛ, significantly affecting the dynamical behavior. Besides, the adjustment of σ and ɛ for nitrile carbon and nitrogen atoms helps reach optimum results. Our refined model shows an excellent agreement with the experiment for self-diffusion coefficient and thermodynamic quantities as well as providing a qualitative description of the microscopic structure of liquid ACN. © 2018 Wiley Periodicals, Inc.