[lammps-users] Looking for a Replacement for CEOS

In principle, MD or Monte Carlo simulations can accurately estimate EOS
properties for arbitrary gas compositions and arbitrary thermodynamic
conditions. In practice, people rarely do so. Here are the reasons that I
can think of, in order of decreasing importance:

1. Interatomic potentials;
    a. These are often developed for condensed phases and so may not be
particularly accurate for gases. For example, the second virial coefficient
at 300K may be off by 10% or more.
    b. They are usually developed for pure species. Mixture interactions are
computed using binary mixing rules, analogous to those used in

2. Statistical uncertainty: These methods are based on statistical sampling,
and so the accuracy converges rather slowly ~ 1/sqrt(CPU time)

3. If all you care about is macroscopic properties, it does not make sense
to use a method that is primarily concerned with microscopic properties.

Given all this, I think you would be better off taking your presumably
accurate pure-component CEOS functions and estimating the necessary binary
mixing parameters, and then using these to describe the multicomponent
mixtures. Don't they teach that in chemical engineering schools anymore?

Finally, always check your results against any available experimental data.

Good luck!