[gmx-users] Modify TIP4P to TIP4P-Ew

[Cai]

Hi users,

The re-parameterized TIP4P-Ew water model shows encouraging agreements with
experimental results. Since it is now not available in GROMACS, I have to
modify the TIP4P water model to TIP4P-Ew according to this paper.

(Horn et. al. (2004). Development of an improved four-site water model for
biomolecular simulations: TIP4P-Ew. *The Journal of Chemical Physics*,
*120*(20),
9665–78).

Q1:
I know how to change the water parameters (angle, rOH, ...) in the topology
file (***.top/itp) and implement the Ewald-summation (coulombtype = PME).
Is that all? It seems the paper also include correction for LJ by
multiplying switching function, adding LJ tail, and correction for
pressure, which are not easy to do in GROMACS. Any suggestions for doing
these?

Q2:
Is it possible to do that without touching the source code?

Does anyone have experience with similar work? Any reply and hint are
highly appreciated!

Caizk