Molecular Dynamics Simulation of Pure n-Alkanes and Their Mixtures at Elevated Temperatures Using Atomistic and Coarse-Grained Force Fields

Abstract

The properties of higher n-alkanes and their mixtures is a topic of significant interest for the oil and chemical industry. However, the experimental data at high temperatures are scarce. The present study focuses on simulating n-dodecane, n-octacosane, their binary mixture at a n-dodecane mole fraction of 0.3, and a model mixture of the commercially available hydrocarbon wax SX-70 to evaluate the performance of several force fields on the reproduction of properties such as liquid densities, surface tension, and viscosities. Molecular dynamics simulations over a broad temperature range from 323.15 to 573.15 K were employed in examining a broad set of atomistic molecular models assessed for the reproduction of experimental data. The well-established united atom TraPPE (TraPPE-UA) was compared against the all atom optimized potentials for liquid simulations (OPLS) reparametrization for long n-alkanes, L-OPLS, as well as Lipid14 and MARTINI force fields. All models qualitatively reproduce the temperature dependence of the aforementioned properties, but TraPPE-UA was found to reproduce liquid densities most accurately and consistently over the entire temperature range. TraPPE-UA and MARTINI were very successful in reproducing surface tensions, and L-OPLS was found to be the most accurate in reproducing the measured viscosities as compared to the other models. Our simulations show that these widely used force fields originating from the world of biomolecular simulations are suitable candidates in the study of n-alkane properties, both in the pure and mixture states.

Diffusivity of α-, β-, γ-cyclodextrin and the inclusion complex of β-cyclodextrin: Ibuprofen in aqueous solutions; A molecular dynamics simulation study

“…To model CDs, we use the q4md-CD force field which has been shown to be very accurate in predicting the crystal properties of CDs [51] . Since it has been shown in literature that the choice of force field to represent the solvent has a significant effect on the computed transport properties of the solutes [52] , [53] , [54] , the diffusion coefficient of CDs are calculated using four different water force fields. After identifying the best performing solute (i.e.…”

The Martini Model in Materials Science

“…Other studies have investigated the self‐assembly and self‐organization of various long‐chain (functionalized) alkanes on surfaces or at interfaces. [ 84,101–107 ] The Martini simulations performed by Piskorz et al. provided a microscopic view on the adsorption and subsequent rearrangement of alkanes on the surface to form long‐range ordered lamellar structures (Figure 3B).…”

A tiny charge‐scaling in the OPLS‐AA + L‐OPLS force field delivers the realistic dynamics and structure of liquid primary alcohols

“…Shear viscosity η is estimated by using the periodic perturbation method (PP-method). 26,27 Briefly, an external force a = (a x , 0, 0) is applied;…”

“…Therefore, the shear viscosity η is obtained as For each alcohol, we apply four acceleration amplitudes (A 0 = 0.010, 0.015, 0.020, and 0.025 nm ps À2 ), analogous to the work for higher n-alkanes. 27 For each A 0 , three independent production NpT-MD runs are performed for each 10 ns, initiating from the well-equilibrated configurations obtained in the calculations for Ds, and each last 8 ns is used for analyses. Then, for each alcohol, the η 0 η 0 ð Þ of unperturbed state is retrieved by extrapolating a linear fitting to η versus A 0 .…”