Comparison of Force Fields for the Prediction of Thermophysical Properties of Long Linear and Branched Alkanes

Abstract

The prediction of thermophysical properties at extreme conditions is an important application of molecular simulations. The quality of these predictions primarily depends on the quality of the employed force field. In this work, a systematic comparison of classical transferable force fields for the prediction of different thermophysical properties of alkanes at extreme conditions, as they are encountered in tribological applications, was carried out using molecular dynamics simulations. Nine transferable force fields from three different classes were considered (all-atom, united-atom, and coarse-grained force fields). Three linear alkanes (n-decane, n-icosane, and n-triacontane) and two branched alkanes (1-decene trimer and squalane) were studied. Simulations were carried out in a pressure range between 0.1 and 400 MPa at 373.15 K. For each state point, density, viscosity, and self-diffusion coefficient were sampled, and the results were compared to experimental data. The Potoff force field yielded the best results.

Structure of the Hexadecane Rotator Phase: Combination of X-ray Spectra and Molecular Dynamics Simulation

“…Unsurprisingly, a large number of molecular dynamics (MD) force fields for alkanes are available with a wide range of potential energy functions and levels of coarse graining, as well as lipid force fields which can be readily adapted. Their performance has been reviewed for reproducing different alkane properties such as liquid phase transport , or phase transition temperatures and solid phase ordering. , Here, we focus on studies looking specifically at modeling of rotator phases for higher alkanes.…”

Investigating the Behavior of Various Lubrication Regimes under Dynamic Conditions Using Nonequilibrium Molecular Dynamics

“…The density of hexadecane calculated by this forcefield under 500 MPa is 890 kg/cm 3 , as shown in ref , which corresponds to the bulk density for n -hexadecane under the same load, according to the Dowson–Higginson equation for the bulk compressibility of liquids . A more accurate version for OPLS forcefield is the L-OPLS force field, which is an optimized version for long linear alkanes and shows significantly better results for predicting thermophysical properties of long linear and branched alkanes than other forcefields . Compared to LOPLS-AA forcefield, OPLS-UA reduces the number of atoms in the system; meanwhile, the computation cost of the C–H bond’s vibration and coulomb interaction is also decreased.…”

“…31 A more accurate version for OPLS forcefield is the L-OPLS force field, 32 which is an optimized version for long linear alkanes and shows significantly better results for predicting thermophysical properties of long linear and branched alkanes than other forcefields. 33 Compared to LOPLS-AA forcefield, OPLS-UA reduces the number of atoms in the system; meanwhile, the computation cost of the C−H bond's vibration and coulomb interaction is also decreased. Harmonic bonds impose restrictions on the atoms in hematite slabs; bonding only happens when the distance between atoms is less than 3 Å.…”

Molecular modeling of interfacial properties of the hydrogen + water + decane mixture in three-phase equilibrium

“…Assessments have shown that all-atom and united-atom models could provide improved accuracy in representing thermodynamic properties over the CG models, as noted in recent benchmark studies. 75,76…”

“…Assessments have shown that all-atom and united-atom models could provide improved accuracy in representing thermodynamic properties over the CG models, as noted in recent benchmark studies. 75,76 Fig. 1 demonstrates equilibrium snapshots of the molecular system for studying the interfacial properties of the H 2 + H 2 O + decane three-phase mixture.…”