I study the sorption of ethylene(or butene) on poly ethylene, i use the materials studio 8.0, in build polymer ten repeat unit was selected , in first geometery optimization was done then the amorphous cell was build and was equilibrated . the sorption modules was selected and ethylene was selected as sorbates . the simulation is ran, and sorption isotherm was zero, is there anyone to tell me why it is zero?do my simulation was wrong?