[gmx-users] (no subject)

[Yongliang Yang]

Dear EB,

Many thanks for the kind reply! We have revised the improper section
followed your advice. The force field is amber99sb. Unfortunately, the
program complained again, "No default proper dih. types'. Any advice?
Thanks!

Cheers

Jeremy



---------------
Hi Jeremy,

I have checked how improper dihedral should look like in Amber, guessing
that you used amber99sb force field. But I am wondering from where the
improper in your ligand.itp was generated. As it doesn not look alike with
the amber force field. It actually is not the problem of multiplicity but
the number of parameters that you put in the improper is not enough. It
should be at least three parameters in the improper section

Yours look like
  [ impropers ]
  CAD  OAX  CAB  CAG       0.000   167.4 (two parameters here angle and
force constant)

Whereas the program is looking for
CT  CT  OS  CT    9       0.0      1.60247     3  (here function, angel,
force constant and multiplicity??) copied from the amber bonded force field
parameter :)

I think you should generate a logical itp file which fullfil all the
necessary requirements before you run you simulation.

Cheers,
EB