[CP2K:3581] general question on calculating metals using cp2k

[carlo antonio pignedoli]

Dear Jun,
regarding the size of the cell, it depends on which property of the
system you would like to reproduce.
There is a simple rule:
if your property is well converged with a k-point cacluation for a
unit cell on a MxM regular grid not shifted (I mean
including Gamma point..)
then a supercell as big as MxM the unit cell will give you "exactly"
the same results.

Of course overriding symmetries could bring the MxM system to a
geomoetry not compatible
with the unit cell (this does not mean that the result is wrong...)
that's in part why I was saying "exactly".


If you are interested in slab calculations, no k-points in the
direction perpendicular to the slab surface,
then the thickness of the slab, again, depends "solely" on the
particular properties of the system that you
would like to reproduce.

For the behavior of the optimization algorithms i let somebody more
expert to reply.

Ciao

Carlo

On Wed, Nov 2, 2011 at 6:35 PM, Jun <chen... at gmail.com> wrote:
> Hi,
>
> I intend to run some calculations on metals. I am wondering if experts
> could give me some ideas on the performance of cp2k. For example, to
> model a metal surface, say Pt(111), what size of the system is big
> enough for compensating the lack of k-point sampling? Usually, how
> many iterations are needed to reach SCF convergence? How long it
> roughly takes for each SCF step? How slow is the matrix
> diagonalisation compared to OT? ...
>
> It would be nice if someone shows me an input example for metals. I
> know there was one given by Prof. Hutter about two years ago. Any up-
> to-date one?
>
> Thanks a lot,
>
> Jun
>
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