problem in sorption module

hi,

i am adsorbing the silver nanopaticles on MCM-41 silica mesoporous material,using sorption module to get adsorption isotherm.

i used Dreiding forcefield ,cvff and all other witch is given in sorption module but all are not working,giving error " The model contains forcefield types that are not part of the selected forcefield." now i am unable to under stand, which forcefield will useful for me?

plzzz tell me which forcefield i should use for my system as soon as possible.

Regards

  Jyoti