Phase state in MC simulation of grand canonical ensemble

[alexam]

Dear all,

checking the output of a Monte Carlo simulation in the grand canonical ensemble, I found "Vapour=stable, Liquid=metastable" stated for each component of a mixture (beginning of the output). This simulation considers water and alcohols in a silica zeolite.

In the manual I could find examples for the same line as "Fluid is a vapour", so I understand it's reporting the phase state of the compound, but I could not find additional explanation to those stable/metastable states.

The only similar citation I could find in the literature (https://pubs.acs.org/doi/10.1021/acsami.8b09343) says that:
"In the case of a hysteresis, for one relative pressure, two states are found. One of the states is a metastable state, and the another is a stable state."

Questions:
a) So, what exactly does RASPA output means with the "Vapour=stable, Liquid=metastable"?
b) Is it somehow related with hysteresis, as mentioned by the article above?

Thanks in advance.
Best regards

[David Dubbeldam]

Based on a Peng-Robinson equation of state it calculates the phase and density of the pure fluid (without framework). This density is used to calculate the excess adsorption.