[gmx-users] Water model choice

Justin Lemkul jalemkul at vt.edu
Mon Jun 17 13:29:56 CEST 2019

On 6/17/19 6:58 AM, Pandya, Akash wrote:
> Hi all,
> Which water model is best to use with the CHARMM27 FF, Tip3p or SPC/E?  I know the CHARMM FF has been optimised with Tip3p, but I also know that SPC/E water model has good agreement with experimental data e.g. diffusion coefficient.
> Any guidance will be much appreciated?

Use the CHARMM-modified TIP3P. You can't look at a water model's 
performance in isolation and just change it. Every force field was 
designed for use with a given water model. There are some instances in 
which this is flexible (e.g. certain water model properties compensating 
for inadequacies in AMBER LJ parameters) but this is not a generally 
applicable practice. If you change the water model, you risk completely 
changing charge screening, therefore subjecting your simulation to 
unpredictable electrostatic artifacts.

Also use CHARMM36 rather than the outdated "CHARMM27" force field. It is 
better in every respect for proteins, lipids, nucleic acids, etc.



Justin A. Lemkul, Ph.D.
Assistant Professor
Office: 301 Fralin Hall
Lab: 303 Engel Hall

Virginia Tech Department of Biochemistry
340 West Campus Dr.
Blacksburg, VA 24061

jalemkul at vt.edu | (540) 231-3129


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