[CP2K:2724] constraint/target

[rupa]

Hi all,
I was trying to understand how the constraint dynamics works in CP2K
for a test case, where water dimer dissociates into H3O+ and OH-. The
constraint was the O---H bond between both the water molecules, which
is expected to decrease from 1.8 to 1.0 Å.
However, the constraint didn't change during simulation.
However, the reverse reaction scheme i.e. H3O+ + OH- -> (H2O)2, where
O-H bond elongates from 1.0 to 1.8 Å, works fine.
It seems the target growth can only be positive!!!
Please correct if I am wrong.

Thanks
Rupa

input reference for constraint section:
&COLVAR
&DISTANCE
ATOMS 1 6
&END DISTANCE
&END COLVAR
&END SUBSYS
******
&CONSTRAINT
&COLLECTIVE
COLVAR 1
INTERMOLECULAR T
TARGET [angstrom] 1.8
TARGET_GROWTH [angstrom*fs^-1] 0.001
TARGET_LIMIT [angstrom] 1.0
&END COLLECTIVE
&LAGRANGE_MULTIPLIERS ON
COMMON_ITERATION_LEVELS 3
&END LAGRANGE_MULTIPLIERS
&END CONSTRAINT


--
You received this message because you are subscribed to the Google Groups "cp2k" group.
To post to this group, send email to cp...@googlegroups.com.
To unsubscribe from this group, send email to cp2k+uns...@googlegroups.com.
For more options, visit this group at http://groups.google.com/group/cp2k?hl=en.

[Teodoro Laino]

Dear Rupa,

the section you have posted:

> &COLVAR
> &DISTANCE
> ATOMS 1 6
> &END DISTANCE
> &END COLVAR
> &END SUBSYS
> ******
> &CONSTRAINT
> &COLLECTIVE
> COLVAR 1
> INTERMOLECULAR T
> TARGET [angstrom] 1.8
> TARGET_GROWTH [angstrom*fs^-1] 0.001
> TARGET_LIMIT [angstrom] 1.0
> &END COLLECTIVE
> &LAGRANGE_MULTIPLIERS ON
> COMMON_ITERATION_LEVELS 3
> &END LAGRANGE_MULTIPLIERS
> &END CONSTRAINT

tells only that you start from a constraint of 1.8 Angstrom and you
increase the constraint of the TARGET_GROWTH amount, Until you reach a
limit of 1.0 Angstrom (in your case the limit is already reached!).

I don't see any problem in the input that you have posted. Maybe you
should try to clarify better your problem.

Teo

[rupa]

Hi Teo,
Thanks for the prompt reply. I am sorry for not being clear enough in
my last mail.
The section below I have used in my input that implies the target to
decrease from 1.8 to 1.0 Angstrom, but in trajectory file I find the
target fixed at 1.8 Å.

TARGET [angstrom] 1.8
TARGET_GROWTH [angstrom*fs^-1] 0.001
TARGET_LIMIT [angstrom] 1.0

But if I increase the target from 1.0 to 1.8 Angstrom, the section
below works fine.
TARGET [angstrom] 1.0
TARGET_GROWTH [angstrom*fs^-1] 0.001
TARGET_LIMIT [angstrom] 1.8

This implies, Target_limit > Target works, but not other way around.
I hope I am clear enough now.

Thanks
Rupa

[Teodoro Laino]

Arithmetics is based on sign!
What about using a "-" in front of 0.001 ?

Teo

[rupa]

Thanks Teo, I shall try that.

[rupa]

Hi Teo,
I got little problem with "Target" again. After using -ve sign for
target growth (keywords below), I do get target limit 1.0 angstrom,
but in the 1st step itself and it remains at 1.0 for rest of the
steps. It does not depend on the step size. This is little strange for
me.

TARGET [angstrom] 1.8
TARGET_GROWTH [angstrom*fs^-1] -0.0001
TARGET_LIMIT [angstrom] 1.0

Please suggest.
Thanks

[Laino Teodoro]

I have no idea what you do: is it so difficult to understand that
partial input files are useless?
The syntax of the posted 3 lines looks correct.
In attachment a test file that works.

Triple check what you are doing : focusing mainly on understanding
what you really do.
I suspect your system is exploding.

Regards and good luck.
Teo

[rupa]

Thank you very much Teo for the valuable suggestion, It was a problem
of version, now works after updating.

> >>>>> +unsub...@googlegroups.com.

> >>>>> For more options, visit this group athttp://groups.google.com/
> >>>>> group/cp2k?hl=en.
>

> >>> --
> >>> You received this message because you are subscribed to the  
> >>> Google Groups "cp2k" group.
> >>> To post to this group, send email to cp...@googlegroups.com.
> >>> To unsubscribe from this group, send email to cp2k

> >>> +unsub...@googlegroups.com.

> >>> For more options, visit this group athttp://groups.google.com/
> >>> group/cp2k?hl=en.
>

> >> --
> >> You received this message because you are subscribed to the Google  
> >> Groups "cp2k" group.
> >> To post to this group, send email to cp...@googlegroups.com.
> >> To unsubscribe from this group, send email to cp2k

> >> +unsub...@googlegroups.com.

> >> For more options, visit this group athttp://groups.google.com/
> >> group/cp2k?hl=en.
>

> > --
> > You received this message because you are subscribed to the Google  
> > Groups "cp2k" group.
> > To post to this group, send email to cp...@googlegroups.com.
> > To unsubscribe from this group, send email to cp2k

> > +unsub...@googlegroups.com.

> > For more options, visit this group athttp://groups.google.com/
> > group/cp2k?hl=en.
>
>
>

>  test_cns.tgz
> 122KViewDownload