GROMACS topology file for the TIP4P/Ice model

The following is a topology file for the TIP4P/Ice model of water for use in the GROMACS computer simulation package.

 [ defaults ]
 ; nbfunc        comb-rule       gen-pairs       fudgeLJ fudgeQQ
 1             2               no              1.0     1.0
 
 [atomtypes]
 ;name     mass      charge   ptype    sigma        epsilon
 IW     0             0.000       D   0.0           0.0
 OWT4   15.99940      0.000       A   0.31668       0.88211
 HW     1.00800       0.000       A   0.00000E+00   0.00000E+00
 
 
 [moleculetype]
 ; name nrexcl
 water  1
 
 [atoms]
 ; nr type resnr residu atom cgnr charge
 1     OWT4 1     water  OW1  1     0          15.994
 2     HW   1     water  HW2  1     0.5897    1.008
 3     HW   1     water  HW3  1     0.5897    1.008
 4     IW   1     water  MW4  1    -1.1794    0.0
 
 [constraints]
 ;i j funct doh  dhh
 1       2       1       0.09572
 1       3       1       0.09572
 2       3       1       0.15139
 
 [exclusions]
 1       2       3       4
 2       1       3       4
 3       1       2       4
 4       1       2       3
 
 ; The position of the dummy is computed as follows:
 ;
 ;               O
 ;
 ;                D
 ;
 ;       H               H
 ;
 ; const = distance (OD) / [ cos (angle(DOH))    * distance (OH) ]
 ;         0.015 nm      / [ cos (52.26 deg)     * 0.09572 nm    ]
 ; Dummy pos x4 = x1 + a*(x2-x1) + b*(x3-x1)
 
 [dummies3]
 ; Dummy from                    funct   a               b
 4       1       2       3       1       0.13458         0.13458  
 
 [system]
 water TIP4P/Ice
 
 [molecules]
 water  1