Dear MS users,

I am trying to change Dreiding force field prior to dynamics (Forcite) calculations. My aim is to calculate Ch4 diffusion (C_34, single atom) in a flexible MOF structure. Prior to MD, I want to perform "geometry optimization" the structure.  I have two basic questions:

1) I open the energy tab in the forcite calculation (task:

geometry optimization) and select the new force field. When I click to more button, which button should I check? If I press "calculate" and then "assign", I see juct C_1 type (force field) for all the atom and when I optimize the structure (using forcite), I see both inversion and torsion with a high energy. However, if I just press calculate and then click, the force field types are C_R, Zn, etc changing and after optimization I see just torsion term with a low energy. I am confused. Which is true? Could you please tell me the procedure for assiging the new force field that we changed?  Why one of them considers inversion as well?

2) When I  look at the torsion tab in the Dreding force field, I do not see kcal/mol values. Does the force field calculates torsion or not? If not, how can I set these dihedral torsion values by using conformer tool or etc for my MOF?

Thank you

ilknur