# This ParmEd script will eliminate all extra points on water and set the
# charges and vdW parameters for water to the TIP3P values. This will
# effectively convert TIP4P(ew) and TIP5P(ew) to TIP3P. All actions act on the
# current, 'active' prmtop. You should have a restart file loaded as well so
# that the coordinates of the EP-less system can be written out, too.

# Use this as <source water_to_tip3p.parmed>

# First strip the extra points
strip :WAT@%EP

# Next change the charges to match TIP3P
change charge @%OW -0.834
change charge @%HW  0.417

# Next change the LJ radii
changeLJSingleType @%HW 0.0 0.0
changeLJSingleType @%OW 1.7926 0.098

# Next change all of the ion parameters to the TIP3P parameters
changeLJSingleType @Li+      1.025     0.0279896
changeLJSingleType @Na+      1.369     0.0874393
changeLJSingleType @K+       1.705     0.1936829
changeLJSingleType @Rb+      1.813     0.3278219
changeLJSingleType @Cs+      1.976     0.4065394
changeLJSingleType @F-       2.303     0.0033640
changeLJSingleType @Cl-      2.513     0.0355910
changeLJSingleType @Br-      2.608     0.0586554
changeLJSingleType @I-       2.860     0.0536816