Thanks Christoph,

I will tweak the min and max.

Chandan


--
Chandan kumar Choudhury
NCL, Pune
INDIA


On Sat, Aug 31, 2013 at 10:03 PM, Christoph Junghans <[email protected]>wrote:

> 2013/8/30 Chandan Choudhury <[email protected]>
> >
> > Dear votca users,
> >
> > I have a small clarifications regarding the tabulated potentials
> (bonded) generated by votca (1.3-dev).
> >
> > The distributions are converted to potentials and the refined and
> extrapolated and then converted to the tabulated potentials. In 1.2.3,
> these processes were manually done.
> >
> > For a spring potential, one would expect the rise in potential for 'r'
> away from minima and this should also be reflected in the tabulated
> potentials.
> >
> > I have attached the bonded distribution and its tab. potentials for
> step_001, what I find is that the tab. potential saturates at large r.
> >
> > I have also attached one of the angle distributions (points exceeding
> 1.1056700000e+02 has been deleted as the value were exactly same. This also
> reduced the file size below 8.0 MB). This angle also shows the spring
> behavior. The similar observation is observed.
> >
> > Is the above behavior normal for spring-type potentials.
> >
> >
> > One more relating to this I could not understand was, when I input a
> spring potential in the topology file, the bond fluctuates around the
> r_minimum. But, when I generate the tabulated potential out of the same
> potential, and now I input this tab. potential, the bond distributions are
> nowhere near to the r_min. Is this normal or something  I am missing. Any
> insight would be of great help.
>
> I had a look at your files and I think I know where your problem are
> coming from!
>
> When Votca does an extrapolation of the potential in the process of
> converting *.pot.cur into *.xvg, it calculated the derivative from the
> last point on each side.In your BDB.angle.pot.cur the first two point
> are equal and hence the extrapolation fails.
>
> I will have to think a bit on how to improve this magic, but for now
> the easiest would be to increase min and decrease max, so that the
> distribution is still bigger 0 for min and max and allow a better
> estimation of the  derivative of the potential.
>
> Christoph
>
> >
> > Chandan
> >
> > --
> > Chandan kumar Choudhury
> > NCL, Pune
> > INDIA
> >
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>
>
>
> --
> Christoph Junghans
> Web: http://www.compphys.de
>
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