Gibbs
Project
CO2
Contents
Models
Three models for CO2 (denoted here as M1, M1b, EPM2)
were compared with published simulation results and experimental data.
Moeller and Fischer determined in Fluid Phase Eq., 100,
(1994) 35-61 a model for CO2 by using two Lennard-Jones
beads plus a point quadrupole. According to this two models for CO2
were constructed by using a combination of two Lennard-Jones beads (with
the molecular weight of oxygen) with the same potential parameters and
three charges (one of them centered with the molecular weigth of carbon,
the other two in a distance z from the center). Model M1 and M1b differ
in the distance z (z=1.061 A for M1, z=0.5305 A for M1b ) and the values
for the charges which were chosen in a way that the quadrupole moment of
Qzz=-12.2*10-20CA2 proposed by Moeller
and Fischer was maintained.
As an alternative the EPM2 model (Harris and Yung, J. Phys. Chem., 99,
(1995)) was used. (Modeling each single atom by a combination of a
Lennard-Jones and a Coulomb potential.) Note that Moeller and Fischer were
using molecular dynamics to obtain their results, Harris and Yung were
using GEMC with reaction field theory instead of Ewald sums.
Phase envelope/Vapor pressure calculation by virtual
volume changes
Four points on the phase envelope of CO2 for temperatures
between 240 K and 295 K were calculated and compared with experimental
data and the simulation results of Moeller and Fischer resp. Harris and
Yung.
rho(T)
The models M1 and EPM2 show good agreement with experimental data for
the vapor phase, for the liquid phase good results are achieved by using
the EPM2 or the M1b model. Vapor pressure calculations for M1, M1b and
EPM2 carbon dioxide were performed at temperatures between 240 K and 295
K and compared with experimental data and the simulation results of Moeller
and Fischer resp. Harris and Yung. Averaging was done over intervals from
1.6*106 to 2.8*106 configurations.
pS(T)
Here very good agreement with experimental data is found for the EPM2 model.
Comparison of the results (numbers)
Last modified by Johannes, July 31st 1996
Page created by Johannes, March 16th 1996
