[gmx-users] spc.itp:HEAVY_H

[Justin A. Lemkul]

Chih-Ying Lin wrote:
> Hi
> In the spc.itp file,
> Is the HEAVY_H = Deuterium  ?
> Then, H2O become D2O ?
> 

No; as you can see from the masses (final column), the hydrogen mass is given as 
4.032 (4x the normal H mass).  The mass of oxygen is also reduced, so you really 
don't have anything close to a real D2O.

Refer to the thread that's actively going on regarding heavy H and a 4-fs 
timestep if you want to read about why you should or should not use heavy 
hydrogen atoms.

-Justin

> Thank you
> Lin
> 
> 
> 
> 
> #ifdef _FF_GROMOS96
> #ifdef HEAVY_H
>      1     OW      1    SOL     OW      1      -0.82    9.95140
>      2      H      1    SOL    HW1      1       0.41    4.03200
>      3      H      1    SOL    HW2      1       0.41    4.03200
> #else
>      1     OW      1    SOL     OW      1      -0.82   15.99940
>      2      H      1    SOL    HW1      1       0.41    1.00800
>      3      H      1    SOL    HW2      1       0.41    1.00800
> #endif
> _______________________________________________
> gmx-users mailing list    gmx-users at gromacs.org
> http://www.gromacs.org/mailman/listinfo/gmx-users
> Please search the archive at http://www.gromacs.org/search before posting!
> Please don't post (un)subscribe requests to the list. Use the 
> www interface or send it to gmx-users-request at gromacs.org.
> Can't post? Read http://www.gromacs.org/mailing_lists/users.php
> 

-- 
========================================

Justin A. Lemkul
Graduate Research Assistant
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

========================================