Improvements and limitations of Mie lambda-6 potential for prediction of saturated and compressed liquid viscosity
Richard A. Messerly, Michelle C. Anderson, S. M. Razavi, J. R. Elliott
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
, Anderson, M.
, Razavi, S.
and Elliott, J.
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 June 5, 2023)