[Pw_forum] Constrained occupation

[Jie Jiang]

On Sat, Nov 6, 2010 at 8:50 AM, Nicola Marzari <
nicola.marzari at materials.ox.ac.uk> wrote:

> On 11/6/10 10:18 AM, Stefano de Gironcoli wrote:
> > Dear Jie,
> >     as Gabriele was saying constrained DFT is not implemented in PWscf:
> > it is not so easy to force occupation of specific atomic-like levels in
> > a plane-wave basis.
>
> Dear Nicola, Stefano,  and Gabriele,
>


> Thank you very much for your information,
>


> One thing I would like to emphasis is that I want to constrain electron
>
    occupations of Kohn-Sham orbitals instead of atomic-like levels. The
    method is usually called Delta-scf DFT,

>
>
    Will this makes some differences in implementation ?

    Thanks in advance,

     Jie



> Dear Jie,
>
> with Patrick Sit and Matteo Cococcioni we did implement constrained DFT
> in the cp code a few years ago - Patrick (cc'd here, now in Princeton)
> has a working version of the code (and hopefully it will at a certain
> point make it into the public distribution).
>
> At the end the procedure is similar to what Stefano has just described -
> one adds a penalty for occupation matrices on a chosen manifold
> that are different from a desired target - by making the penalty very
> large one can make it into an exact constraint, or one could impose
> directly a Lagrange multiplier.
>
> Any code that has a working version of DFT+U should be easy to
> modify to make it into constrained DFT - you change the orbitals
> onto which you make the projections, and add a penalty or a
> Lagrange multiplier to force approximately or exactly the constraint
> that you want.
>
>                                nicola
>
>
>
>
> PS: H.-L. Sit, M. Cococcioni, and N. Marzari, "Realistic, Quantitative
> Descriptions of Electron-Transfer Reactions: Diabatic Surfaces from
> First-Principles Molecular Dynamics," Phys. Rev. Lett. 97, 028303
> (2006).
>
> Sit P. H.-L., Cococcioni M., Marzari N. "Car-Parrinello molecular
> dynamics in the DFT+U formalism: Structure and energetics of solvated
> ferrous and ferric ions" Journal of Electroanalytical Chemistry 607,
> 107-112, (2007)
> --
> ----------------------------------------------------------------------
> 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
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