[lammps-users] Vibrating or moving CO2 molecules?

The temperature and the pressure that i have used correspond to vapor state.

but have you thought about the fact that when you create your
initial geometry with high (non-gas phase) density, that your
system could be trapped in the liquid or solid phase. also, if
you do a minimization this will be equivalent to "quench" your
system to a zero kelvin state.

to get out of there, you will have to "insert" the heat of
vaporization (or rather sublimation in the case of CO2)
or else your system will be meta-stable (and can be for
a long time). small finite size systems don't always behave
like bulk systems and the time scales are very short, too.