[gmx-users] TIP4p water in gromos force field files (OWT4 and IW)??

[Justin A. Lemkul]

Rasmus Lundsgaard wrote:
> Dear all
> 
> I would like to do some simulation with the TIP4p water model with the 
> ffG53a6 (Gromos96) force field.
> 
> In *TIP4p.itp* it states to use the *OWT4* atom for the oxygen and the 
> *IW* for the charged atom (4 site water model), but these two atoms are 
> not listed in the *ffG53a6nb.itp* and *ffG53a6bon.itp* files. This means 
> that GROMACS can not find these atoms and how to calculate LJ and bonded 
> forces with these atoms...
> 
> Have I overseen something or are they suddenly lost from the gromos 
> itp's in GROMACS??
> 
> The OW atom in the itp's are for the SPC/E water model - so they are not 
> use able for TIP4p (different LJ parameters)

I don't know that I've seen anyone do a simulation with Gromos96+TIP4P.  The 
original derivation of Gromos96 (and the most common usage) is Gromos96+SPC or 
SPC/E.  If you're set on using TIP4P as your water model, you'd better be ready 
to provide justification for that choice.

If you need to add atom types, you certainly can, but you may have to re-name 
them so as not to conflict with existing SPC or SPC/E atom types.  It's very 
simple to put these parameters in the nb.itp, bon.itp, and .atp files.

-Justin

> 
> 
> Best regard!
> Rasmus
> 
> -- 
> PhD student at "Center for Energy Resources Engineering" (CERE-DTU)
> Department of Chemical and Biochemical Engineering, Building 229
> Technical University of Denmark - DTU
> DK - 2800 Lyngby, Denmark
> Email: RAL at kt.dtu.dk
> 

-- 
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Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
MILES-IGERT Trainee
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

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