Improvements and limitations of Mie lambda-6 potential for prediction of saturated and compressed liquid viscosity

Published

November 2, 2018

Author(s)

Richard A. Messerly, Michelle C. Anderson, S. M. Razavi, J. R. Elliott

Abstract

Over the past decade, the Mie lambda-6 (generalized Lennard-Jones) potential has grown in popularity due to its improved accuracy for predicting vapor-liquid coexistence densities and pressure compared to the traditional Lennard-Jones 12-6 potential. This manuscript explores the hypothesis that greater accuracy in characterizing the coexistence properties may lead to greater accuracy for viscosity predictions. Four united-atom force fields are considered in detail: the Transferable Potential for Phase Equilibria (TraPPE-UA) model of Siepmann and coworkers, the Transferable Anisotropic Mie (TAMie) model of Gross and coworkers, the fourth generation anisotropic-united-atom (AUA4) model of Ungerer and coworkers, and the model of Potoff and coworkers. Equilibrium molecular dynamics simulations are analyzed using the Green-Kubo method for viscosity characterization. Simulations are performed for linear alkanes with two to twenty-two carbons and branched alkanes with four to nine carbons. Simulation conditions follow the saturated liquid from reduced temperatures of 0.5 to 0.85 and along the 293 K isotherm in the dense liquid region. In general, the more accurate force fields for coexistence properties do indeed predict viscosity more accurately. For saturated liquids, both Mie-based potential models (Potoff and TAMie) provide roughly 10% accuracy for linear alkanes, while deviations are closer to 20 to 50% for TraPPE-UA. For branched alkanes, the performance is slightly diminished but Potoff still provides roughly 15 to 20% accuracy, while the TAMie force field results in deviations of 20 to 40%, and TraPPE-UA has deviations of approximately 25 to 60%. The AUA4 deviations are 10 to 20% for ethane and 30 to 60% for 2,2-dimethylpropane, the only compounds tested with the AUA4 force field. The TraPPE-2 deviations for ethane are similar to those using the original TraPPE force field, namely, between 10 and 20%. The percent deviations for each compound and force fie

Citation

Fluid Phase Equilibria

Pub Type

Journals

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Keywords

Thermophysical Properties, Molecular Simulation, Force Fields, Molecular Dynamics, Green-Kubo

Citation

Messerly, R. , Anderson, M. , Razavi, S. and Elliott, J. (2018), Improvements and limitations of Mie lambda-6 potential for prediction of saturated and compressed liquid viscosity, Fluid Phase Equilibria, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=926488 (Accessed December 11, 2024)