[CPMD-list] Is it possible to keep the POINT GROUP fixed in geometry optimization and any molecular dynamics?

[Axel Kohlmeyer]

On 6/11/06, osirixu-cpmd at yahoo.com.cn <osirixu-cpmd at yahoo.com.cn> wrote:
> Dear cpmders,
>
>     It seems to me in a geometry optimization
> (geo-opt) and any md process, the SYMMETRY can be
> fixed if the keyword SYMMETRY is indicated; But when

dear rex,

please check the manual again:

http://www.cpmd.org/manual/node44.html#SYMMETRY

the SYMMETRY keyword defines the bravais lattice used,
and thus the geometry of your supercell.

> the keyword POINT GROUP is also indicated, the POINT
> GROUP is still changing in the geo-opt and md
> simulation: we can check this by restarting the same
> job from the previous running.

please check the output, whether your input is actually
read correctly. or better yet, please post a small(!) example
that reproduces what you want to do but does not work,
so that we can actually have a look and see what is wrong.

> To my understanding, this means the system is not
> fully equilibrated, but I just wish the POINT GROUP
> could keep fixed during the pre-equilibration. Is
> there any way to make this?

that depends a bit on your system, but for many typical
cpmd problems, people actually use constraints or restraints
to preserve certain structural elements.

axel.
>
>
>     Many Thanks!
>
>        Rex
>     May 27, 2006
>
>
>
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-- 
=======================================================================
Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
  Center for Molecular Modeling   --   University of Pennsylvania
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