SAT-TMMC: Liquid-Vapor coexistence properties - TraPPE Carbon Dioxide
Liquid-vapor coexistence properties of Carbon Dioxide, modeled by the TraPPE Force Field , obtained by grand-canonical transition-matrix Monte Carlo and histogram re-weighting. Mean values of the saturation pressure, density, and activity (chemical potential- see below) for each phase are reported.
|METHOD||Grand-canonical transition-matrix Monte Carlo  and histogram re-weighting|
|Lennard-Jones||15 Å + analytic Long-range Corrections|
|Electrostatics||15 Å + Ewald Summation|
|Prob. of Disp. Move||0.3|
|Prob. of Rot. Move||0.2|
|Prob. of Ins/Del Move||0.5|
|Biasing Function Update Frequency||1.0E6 trial moves|
|Simulation Length||1.0E9 trial moves|
Uncertainties were obtained from four independent simulations and represent 95% confidence limits based on a standard t statistic. Liquid-vapor coexistence was determined by adjusting the activity such that the pressures of the liquid and vapor phases were equal. Here, the pressure is not the conventional virial pressure [3,4] but is the actual thermodynamic pressure, based on the fact that the absolute free energies can be obtained from the distributions determined from simulation . Alternative methods, for example Gibbs-ensemble Monte Carlo and combination grand-canonical Monte Carlo and histogram re-weighting, can be used to determine liquid-vapor coexistence. A review of standard methods of phase equilibria simulations can be found in Ref. 6.
z = Λ-3 exp(βμ)
where Λ is the de Broglie wavelength, β = 1/(kBT) (where kB is Boltzmann's constant), and μ is the chemical potential. It is sometimes more convenient to work with ln z in the simulations and in post-processing. The reported activity has units of Å-3.
- J. A. Potoff and J. I. Siepmann, AIChE J., 47, 1676–1682 (2001).
- J. R. Errington, J. Chem. Phys. 118, 9915 (2003).
- M. P. Allen and D. J. Tildesley, Computer Simulation of Liquids (Oxford University Press, New York, 1989).
- D. Frenkel and B. Smit, Understanding Molecular Simulation, 2nd ed. (Academic, San Diego, 2002)., pp.37-38.
- J. R. Errington and A. Z. Panagiotopoulos, J. Chem. Phys., 109, 1093 (1998).
- A. Z. Panagiotopoulos, J. Phys.: Condens. Matter, 12, R25-R52, (2000).