4
      1 OICE   0.0000000000E+00   0.0000000000E+00   0.0000000000E+00
      2 HICE   0.9572000000E+00   0.0000000000E+00   0.0000000000E+00
      3 HICE   -.2399872084E+00   0.9266272065E+00   0.0000000000E+00
      4 MICE   0.9652490078E-01   0.1247085945E+00   0.0000000000E+00

# TIP4P-2005 Water model
#
# J. L. F. Abascal, E. Sanz, R. G. Fernández, C. Vega
# J. Chem. Phys., 2005, 122, 234511.


# The position of the dummy is computed as follows:
#
#               O
#             / | \
#            /  M  \
#           /       \
#          H         H
#
# const = distance (OD) / [ cos (angle(DOH))    * distance (OH) ]
#         0.01577 nm    / [ cos (52.26 deg]     * 0.09572 nm    ]
#
# Dummy pos x4 = x1 + a*(x2-x1) + b*(x3-x1)



# LAMMPS TIP4P MODEL (Dist O-M,  Oxygen charge)
TIP4P     0.1577   -1.1794

# Constrain UNITS
CONSTRAINS 1 append
  2        3

IFDLP
        RIGID 1
        4 1 2 3 4
ENDIF

# VIRTUAL SITES
VS3     1
4    1  2  3  1   0.13458335  0.13458335

ATOM      1  O1                  0.000   0.000   0.000
ATOM      2  H2                  0.957   0.000   0.000
ATOM      3  H3                 -0.240   0.927   0.000
ATOM      4  M4                  0.097   0.125   0.000