[gmx-users] Water models and force fields

[Lieven Buts]

David wrote:
> This is a difficult topic, only testing can give you the answer. We have
> done some tests for peptides in different water models (J. Biomol. NMR
> 8, (1996) 229-238) and for pure water in different models (JCP 108
> (1998) 10220-10230). There are some other published comparisons too In
> general TIP3P should be avoided, TIP4P and SPC are decent, whereas SPC/E
> and TIP5P are only suitable for highly polar systems such pure water or
> maybe salt solutions.

Just to make sure: what would need to be done to use TIP4P instead of
SPC?
I presume you have to run

   genbox -cp out.gro  -cs tip4p.gro   -o solv.gro   -p whatever.top
                       =============

although this gives the following strange warning:

WARNING: masses will be determined based on residue and atom names,
         this can deviate from the real mass of the atom type
Opening library file
/nurvt/programs/IRIX64_IP30/specific/gromacs-3.1.4/share/top/atommass.dat
Mass of atom SOL MW4 set to 12.011
==================================


Then the section 

; Include water topology
#ifdef FLEX_SPC
#include "flexspc.itp"
#else
#include "spc.itp"
#endif

would have to be changed, but I do not know exactly how.


-- 
Lieven Buts
Vrije Universiteit Brussel