[Pw_forum] makov-payne or ee
Stefano de Gironcoli
degironc at sissa.it
Tue Nov 17 12:10:13 CET 2009
there are two ways you can calculate an isolated system using version
4.1.1 (three if you use cvs verison)
Using 4.1.1:
- Makov-Payne: just define assume_isolated = .true. the code calculate
an estimate of the energy correction for the presence of images. This
does not introduce a correction for the potential (except a constant
shift if i recall correctly).
The correction is calculated from the Madelung constant of the Bravais
lattice used so there is no constraint on that.
-dcc: density counter charge correction (using ee) define do_ee as
.true. and then the needed variables in the auxiliary ee namelist
(please refer to the INPUT_PW.html etc for a description) . The
multigrid solver only works for orthorhombic cells.
If you are using CVS version. one additional option has been added and
the input restructured (simplified?)
assume_isolated is now a CHARACTER variable whose choices are:
'none' (default): regular periodic calculation w/o any correction.
'makov-payne', 'm-p', 'mp' : the Makov-Payne correction to the
total energy is computed. An estimate of the vacuum
level is also calculated so that eigenvalues can be
properly aligned.
Theory:
G.Makov, and M.C.Payne,
"Periodic boundary conditions in ab initio
calculations" , Phys.Rev.B 51, 4014 (1995)
'dcc' : density counter charge correction.
The electrostatic problem is solved in open boundary
conditions. At variance with the Makov-Payne approach
that only estimates an energy correction here the
scf potential is corrected as well.
The OBC problem is solved useing a multi-grid algorithm
that requires additional input provided in the separate
namelist EE (see later).
Theory described in:
I.Dabo, B.Kozinsky, N.E.Singh-Miller and N.Marzari,
"Electrostatic periodic boundary conditions and
real-space corrections", Phys.Rev.B 77, 115139 (2008)
'martyna-tuckerman', 'm-t', 'mt' : Martyna-Tuckerman correction.
As for the dcc correction the scf potential is also
corrected. Implementation adapted from:
G.J. Martyna, and M.E. Tuckerman,
"A reciprocal space based method for treating long
range interactions in ab-initio and force-field-based
calculation in clusters", J.Chem.Phys. 110, 2810 (1999)
--
Please have a look at the theory papers before using a given option so
that you know what you are doing.,
The correction is VERY important for charged system. It is less
critical, still usefull, for neutral molecules, especially when
significant dipoles are present.
Check convergence w.r.t to cell size and compare yourself the
different approaches.
best regards,
stefano
ali kazempour wrote:
> Hi All
> I want to do charged calculation in a supercell that is not cubic. I
> saw esspresso can do makov-payne by " asuume_isolated=.true' in
> periodic boundary condition and also do ee in open boundary condition.
> Since my supercell is not cubic how can I use makov-payne for
> non-cubic supercell.?
> Can I use ee to correct the energy in the case of charge calculation?
> thanks a lot
>
> Ali Kazempour
>
> Fritz-Haber-Institut fax : ++49-30-8413 4701
> der Max-Planck-Gesellschaft
> Faradayweg 4-6 e-mail: kazempou at fhi-berlin.mpg.de
> D-14 195 Berlin-Dahlem / German
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>
More information about the users
mailing list