 For the remaining two systems, BEA and FAU, the heats of adsorption are rather low at low pressures, but increase significantly with increasing pressure. A qualitatively similar evolution has been observed experimentally for TCE in siliceous zeolite Y, although the overall increase was not quite as pronounced as predicted by the simulations reported here. In FAU, the large cages put few constraints on the position and orientation of the adsorbed molecules, allowing for local arrangements that maximize attractive guest-guest interactions.