[gmx-users] Van der Waals: switch attractive term off
Pradip Kumar Biswas
p.biswas at csuohio.edu
Mon Jul 3 16:42:30 CEST 2006
On Jul 1, 2006, at 3:24 AM, Mark Abraham wrote:
>> It seems that you can modify the following line in the function
>> *mk_nbfp() in force.c and achieve what you want.
>> C6(nbfp,atnr,i,j) = idef->iparams[k].lj.c6; (it is in line 117
>> of force.c in version 3.3)
>> and change it to
>> C6(nbfp,atnr,i,j) = 0;
>> This will set the attractive interaction between atom i & j to 0.
> More correctly, it will set the coefficient of the r^6 term to zero.
That's the goal.
> alters the shape of the function for *all* r, both in the "attractive"
> "repulsive" regions,
I could not get that. How could the setting C6(nbfp,atnr,i.j) = 0 can
affect the repulsive interaction term, keeping in mind that even if
you are using a ff that uses 'sigma' or 'epsilon' to construct C6 and
C12 and explicit the minimum of the potential, you are not affecting
> such that the potential function no longer has a
> local minimum.
That's true and that's possibly be the concern of the user who wanted
only to switch-off the attractive (c6) vdw without asking for its
> As Erik pointed out, this is very different from having
> zero force after a certain r.
> gmx-users mailing list gmx-users at gromacs.org
> 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
Pradip K. Biswas, PhD.
Research Associate, Department of Chemistry;
Cleveland State University, Ohio-44115
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Size: 1880 bytes
Desc: not available
More information about the gromacs.org_gmx-users