Hi Sirs/Madams

I wish to estimate the effect of colloid size, geometry and packing in amorphoue silica gel, on the adsorption of CO2. Please how do I create the simulation box made up of a paticular number of colloid particles(made up of Si and O atms), with a specified density. Adsorption simulation is to be carried out on the amount of surface and pore volume available. I can't really figur out how to treat this. Please kindly enlighten me, I will be most greatful. Thanks.