[Pw_forum] makov-payne or ee

[Stefano de Gironcoli]

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
>
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