3

    1 HW  -0.958056233366E+00  -0.541711252568E-01   0.000000000000E+00
    2 OW   0.419437666341E-01  -0.541711252568E-01   0.000000000000E+00
    3 HW   0.292323770689E+00   0.913976515121E+00   0.000000000000E+00

#
#               OW
#              /  \
#            HW    HW
#
#
# Force Field by:
#
# H.J.C. Berendsen, J.P.M. Postma, W.F. van Gunsteren, J. Hermans 
# Intermolecular Forces, ed B. Pullman, Dordrecht: Reidel, 1981, p. 331.

# TIP: running the simulation with rigid molecules is faster than using
# constrains. However, if Pakmol is used, a quaternion error is obtain.
# To solve this problem, run a small simulation (e.g. 5 steps) using 
# contrains and then you can switch the force field for rigid molecules.


# Constrain UNITS
CONSTRAINS 1 append
  1        3


ATOM      1  H_+                -0.958  -0.054   0.000
ATOM      2  O2                  0.042  -0.054   0.000
ATOM      3  H_+                 0.292   0.914   0.000