[MMTK] TIP4P water potential in MMTK

[Andreas Kring]

Hello again,

Is it possible to implement the TIP4P water potential (Jorgensen et al., 
J. Chem. Phys, 79(2), 926 (1983)) into the Amber force field in MMTK 
instead of TIP3P, which is the standard water potential?

This requires that one must specify charges and force constants for 
hamonic oscillators etc., for points that are not located on atoms, 
which seems not to be possible in MMTK (when reading through the 
"Constructing the Database" section in the MMTK manual)?

Is it possible to construct a water molecule in the database that 
contains a mass-less atom (then one can specify charges for this in the 
database file and force constants in the Amber database)?

Kind regards
Andreas