  In this work we report studies of nitrogen adsorption and desorption onto
solid surfaces using computer simulations of the three dimensional Ising model,
for systems with complex porous structures at the mesoscopic and microscopic
levels. A hysteresis cycle between the adsorption and desorption processes
appears and we find that its characteristics are dependent on the geometry of
the pore and on the strength of the surface fluid interaction. We obtained also
an average adsorption isotherm, which represents a combination of differently
shaped pores, and shows robust jumps at certain values of the chemical
potential as a consequence of the structures of the pores. Lastly, we compare
our results with experimental data and also report the filling process of
microscopic pores connected with mesopores. It is argued that these predictions
are useful for researchers working on the enhanced recovery of oil and for the
design of new nanomaterials, among others.
