[gmx-users] How to run multiple (different) distance restrains in the same simulation?

[Tanos Franca]

Dear users,

     I´m trying to run a MD simulation using different distance restraints
for several pairs of atoms in a large ligand (example: 0.1 nm - 0.2 nm; 0.2
nm
- 0.3 nm, ...) but it´s not working. GROMACS is only accepting one range of
restraint (example: 0.1 nm - 0.2 nm for all pairs) per simulation. If
I try including different ranges I get the fatal error message bellow.
     I'm doing it according to item 4.3.5 of GROMACS manual and including
the distance restrains in the .itp file of the ligand as described below.
    Does someone knows how to run the different range of distances in the
same MD simulation?
     Bests,
     Tanos França.

-------------------------------------------------------
Program gmx grompp, VERSION 5.1.4
Source code file:
/home/cuda1/Downloads/gromacs-5.1.4/src/gromacs/gmxpreprocess/readir.c,
line: 3872

Fatal error:
Found 2 double distance restraint indices,
probably the parameters for multiple pairs in one restraint are not
identical

For more information and tips for troubleshooting, please check the GROMACS
website at http://www.gromacs.org/Documentation/Errors
-------------------------------------------------------

[ distance_restraints ]
; ai       aj     type     index     type'     low     up1     up2     fac
  54      33        1         0         1     1.8     1.8     2.5     1.0
  64      63        1         0         1     2.5     2.5     3.5     1.0
  25      65        1         0         1     2.5     2.5     3.5     1.0
  34      42        1         0         1     2.5     2.5     3.5     1.0
  63      14        1         0         1     2.5     2.5     3.5     1.0
  53      25        1         0         1     3.5     3.5     4.5     1.0
  14      62        1         0         1     3.5     3.5     4.5     1.0
  14      13        1         0         1     3.5     3.5     4.5     1.0
  54      34        1         0         1     3.5     3.5     4.5     1.0