[gmx-users] Verlet AND tabulated potential

[Tamas Karpati]

Dear all,

I have trouble creating a FF without bonds explicitely defined,
only using "nonbonding" forces of the Buckingham (BH) type to keep
my crystal in one piece. The problem is related to wrong interatomic
forces on basis of the ASCII-dumped TRR files. So FF works (at
least functionally), optimization does not.

Since replacement of BH by an approximate LJ potential succeeded
I decided to by-pass the built-in BH code by a tabulated potential.
Unfortunately, GROMACS (versions 4.6.3, 4.6.5, 5.0-beta2 and 5.0)
wouldn't take my MDP file.

I kindly ask your help on the subject. The typical error message
is coming from GROMPP in the forms:

  1. "With Verlet lists only cut-off and PME LJ interactions are supported"
  2. "With Verlet lists only cut-off, reaction-field, PME and Ewald
  electrostatics are supported"

Never mind the LJ statement above as the same appears with BH, as well.
The forcefield.itp/[default] contains nbfunc=2 and comb-rule=1.

The connected part of the MDP file is
  "...
  cutoff-scheme   = verlet
  vdwtype = User
  coulombtype = User
  ..."

I seem to be incompatible (in fact new to) GROMACS or User does not
much like Verlet cut-offs. I'm stuck. If you have any idea or working
example, please share it. I'v failed locating relevant info on the Internet
so far.

Thanks in advance,
   toma