[gmx-users] FEP and position restraints

[P]

Hi all
I'm doing FEP calculation on Zn ions.
Is three a way to put position restraints 
on perturbated / dummy  atoms.
When I define in my system.top:

.
.
#include "zn.itp"
[ position_restraints ]
;  i funct       fcx        fcy        fcz
   1    1       1000       1000       1000

#include "cl.itp"
[ position_restraints ]
;  i funct       fcx        fcy        fcz
   1    1       1000       1000       1000

#include "dum.itp"
[ position_restraints ]
;  i funct       fcx        fcy        fcz
   1    1       1000       1000       1000

[ system ]
 .. 
.
..


I'm perturbating Zn ions into dummy atoms. 
 (I'm using ffgmx I've added new DUM atomtype)
When I use grompp I get following warning:

..
..
checking input for internal consistency...
calling /lib/cpp...
processing topology...
Generated 1238 of the 2080 non-bonded parameter combinations
WARNING 1 [file "system.top", line 11]:
  No default Position Rest. types for perturbed atoms, using normal values
WARNING 2 [file "system.top", line 21]:
  No default Position Rest. types for perturbed atoms, using normal values
Excluding 3 bonded neighbours for Protein 1
turning H bonds into constraints...
..
..

How can I apply position restraints on them.  
Please give me some comment on this and thank you in advance!!
All best. 
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