[gmx-users] problem in distance restraint

[Masomeh Dehghani]

Dear users
 
 I have 6 water molecules ,I want to constraint the distance between 6 oxygen  atoms in 0.42 nm  from together.I read GROMACS manual but I had fatal erorr.
 
Here there is  disres.itp file:
 
; Include Distance restraints file
#ifdef DDISRES
#endif
[ distance_restraints ] 
;ai     aj      type    index   type'   low     up1     up2     fac
 1      4         1       1       1      0.42    0.42    0.42    2.0
 1      7         1       2       1      0.42    0.42    0.42    2.0
 1      10        1       3       1      0.42    0.42    0.42    2.0
 1      13        1       4       1      0.42    0.42    0.42    2.0
 1      16        1       5       1      0.42    0.42    0.42    2.0
 
my topology file:
; Include Distance restraint file
#ifdef DISRES
#include "disres.itp"
#endif

my  em.mdp
define         = -DDISRES
disres         = simple
 
error
WARNING 1 [file em.mdp, line 19]:
  Unknown left-hand 'disres' in parameter file
 
Please give me some advice
Thank you
 
Mona
Ph.D student 
University of Tehran
Iran
098-9360213608