[gmx-users] VDW switched off in CHARMM tip3p model

[Weilong Zhao]

Hi,

I noticed that for GROMACS versions of 4.5 of later, the force field for
TIP3P water model in CHARMM27.ff package has a following line included:

 The following atom types are NOT part of the CHARMM distribution
..
.
HWT3    1       1.008000        0.417   A       0.0     0.0     ; TIP3p H

It seems that VDW interaction of the default hydrogen of water is switched
off, which makes it not the correct TIP3P ff of CHARMM. However this
hydrogen type HWT3, is used as default by gromacs as CHARMM water model.

Even though the hydrogen without VDW is the original TIP3P water model, I
wonder is there any problem to include it in CHARMM ff set? Really
appreciate if anyone could share some opinion.

-- 
*Wei-Long Zhao*
Graduate Student
Sahai's Research Group* *
Department of Polymer Science
Goodyear Polymer Center RM 631
University of Akron
170 University Ave.
Akron, OH 44325
Phone:330-972-3026