[Pw_forum] Car-Parrinello of metal surface

[Nicola Marzari]

Dear Sara,


the CP algorithm breaks down in the limit of a vanishing gap -
see the Pastore Smargiassi Buda 1991 PRB, or the Mauri Tassone
Car from a few years later (or the books on the topic - e.g. the
Marx Hutter is the best reference).

Hence you need to do a Born-Oppenheimer minizimation at every ionic
time step - within the CP code it is implemented using the ensemble-dft
algorithm we developed years ago (PRL 1997); see example29, at least
for the electronic part.

Or you could use PWSCF, and perfrom a BO molecular dynamics. In 
principle the CP codes is more suitable to large-scale simulations, and
the ensemble-DFT algorithm is very robust, but it has never been really
optimized (still, we are currently doing simulations on ~200 atom
metallic slabs).

			nicola



On 6/1/11 3:58 PM, Sara Furlan wrote:
> Dear All,
>
> I would like to perform a Car-Parrinello molecular dynamics with cp.x
> code (version 4.3.1)
> on a metallic system (alloy surface).
> I verified that if you specify
> electron_dynamics = 'verlet'
> the only possible electron occupations are fixed, witch is not very
> suitable for a metal
> system.
>
> Can Anybody confirm what I have just affirmed?
> Could Anybody suggest me how to perform a CP molecular dynamics of metal
> surface?
>
> Best regards,
>
> Sara Furlan
>
> Department of Physics, University of Trieste (Italy)


-- 
----------------------------------------------------------------------
Prof Nicola Marzari    Department of Materials    University of Oxford
Chair of Materials Modelling  Director, Materials Modelling Laboratory
nicola.marzari at materials.ox.ac.uk     http://mml.materials.ox.ac.uk/NM