Application of the TraPPE force field to predicting isothermal pressure-volume curves at high pressures and high temperatures

Becky L. Eggimann, J. Ilja Siepmann, Laurence E. Fried

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Knowledge of the thermophysical properties of materials at extreme pressure and temperature conditions is essential for improving our understanding of many planetary and detonation processes. Significant gaps in what is known about the behavior of materials at high density and high temperature exist, largely, due to the limitations and dangers of performing experiments at the necessary extreme conditions. Modeling these systems through the use of equations of state and particle-based simulation methods significantly extends the range of pressures and temperatures that can be safely studied. The reliability of such calculations depend on the accuracy of the models used. Here we present an assessment of the united-atom version of the TraPPE (transferable potentials for phase equilibria) force field and single-site exp-6 representations for methane, methanol, oxygen, and ammonia at extreme conditions. As shown by Monte Carlo simulations in the isobaric-isothermal ensemble, the TraPPE models, despite being parameterized to the vapor-liquid coexistence curve (i.e., relatively mild conditions), perform remarkably well in the high-pressure/high- temperature regime. The single-site exp-6 models can fit experimental data in the high-pressure/temperature regime very well, but the parameters are less transferable to conditions below the critical temperature.

Original languageEnglish (US)
Pages (from-to)796-804
Number of pages9
JournalInternational Journal of Thermophysics
Issue number3
StatePublished - Jun 2007

Bibliographical note

Funding Information:
Acknowledgments Financial support from the National Science Foundation (CTS-0553911 and ITR-0428774) is gratefully acknowledged. Part of this work was performed under the auspices of the US Department of Energy by the Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48. Part of the computer resources were provided by the Minnesota Supercomputing Institute.


  • Equation of state
  • Extreme conditions
  • Monte Carlo simulation
  • Transferable force field


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