Effect of varying the 1–4 intramolecular scaling factor in atomistic simulations of long-chain N-alkanes with the OPLS-AA model
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A comprehensive molecular dynamics simulation study of n-alkanes using the optimized potential for liquid simulation with all-atoms (OPLS-AA) force field at ambient condition has been performed. Our results indicate that while simulations with the OPLS-AA force field accurately predict the liquid state mass density for n-alkanes with carbon number equal or less than 10, for n-alkanes with carbon number equal or exceeding 12, the OPLS-AA force field with the standard scaling factor for the 1–4 intramolecular Van der Waals and electrostatic interaction gives rise to a quasi-crystalline structure. We found that accurate predictions of the liquid state properties are obtained by successively reducing the aforementioned scaling factor for each increase of the carbon number beyond n-dodecane. To better understand the effects of reducing the scaling factor, its influence on the torsion potential profile, and the corresponding gauche-trans conformer distribution, heat of vaporization, melting point, and self-diffusion coefficient for n-dodecane were investigated. This relatively simple procedure enables more accurate predictions of the thermo-physical properties of longer n-alkanes.
KeywordsAlkanes Chain stiffness Intramolecular interaction Molecular dynamics OPLS Scaling factor
This work was supported by the US Department of Energy, Office of Nuclear Energy under the Nuclear Energy University Program (DOE-NEUP), contract number: DE-AC07-051D14517. Computing resources used at the Center for Advanced Modeling and Simulation at the Idaho National Laboratory through a collaboration with the Nuclear Energy Advanced Modeling and Simulation program of the Nuclear Energy Office of DOE are greatly appreciated. The Oak Ridge National Laboratory is managed by UT-Battelle, LLC for the DOE under contract No. DE-AC05-00OR22725.
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