[gmx-users] Nonbonded parameters

[Steven Neumann]

Dear Gmx Users,

Please, correct me if I am wrong. In ffnonbonded.itp

[ atomtypes ] - these are nonbonded parameters between atoms of the same
type
[ nonbond_params ] these are nonbonded parameters between atoms of
different type
[ pairtypes ] - 1-4 interactions

If that is correct why amber force filed has only [atomtypes] column? How
nonbonded parameters are calculated between atoms of a different type?
The same with charmm - only [atomtypes ] and [pairtypes ] are provided.
Would you please explain?

Steven