Enthalpy of adsorption for binary mixture

[AHF]

Hello RASPA community,

I wonder if enthalpy of adsorption of individual components in a binary mixture can be reliably computed using the fluctuation formula?

I am simulating a system for competitive adsorption of CH4 and N2 in NaY zeolites using the GCMC technique. Although RASPA can calculate "total enthalpy of adsorption" correctly, it returns "-nan" values for enthalpy of adsorption of each component in the mixture (i.e. CH4 and N2).

I wonder if anyone has a clue why this is the case? Is this a RASPA problem or the fluctuation formula cannot be used for this purpose?

Many thanks in advance.
     

[David Dubbeldam]

The fluctuation formula has to be used in the grand-conical ensemble, i.e. the molecules must fluctuate.
Numerical problems might also occur at high loadings where the lack of accepted insertions/deletions can become a problem.