[CPMD-list] External Potential keyword

[Juerg Hutter]

Hi

if you have a look in the file exterp.F you can see
that there are two versions of the input. The old
(now disabled) version was reading an ASCII file,
the new version reads a binary file.

You are reading the array EXTPOT, PSCR is only needed
for parallel runs as intermediate memory.

This code would write an acceptable file

REAL*8  EXTPOT(NR1S,NR2S,NR3S)
DO IX=1,NR1S
  DO IY=1,NR2S
    WRITE(xx) (EXTPOT(IX,IY,IZ),IZ=1,NR3S)
  ENDDO
ENDDO

The values of NR1S,NR2S,NR3S you find in the CPMD output
in section SUPERCELL

REAL SPACE MESH:   NR1S NR2S NR3S

All units are "atomic". Be careful to have the right
definition of the origin, (1,1,1) or (N/2,N/2,N/2).

regards

Juerg

----------------------------------------------------------
Juerg Hutter                   Phone : ++41 1 635 4491
Physical Chemistry Institute   FAX   : ++41 1 635 6838
University of Zurich           E-mail: hutter at pci.unizh.ch
Winterthurerstrasse 190
CH-8057 Zurich, Switzerland
----------------------------------------------------------


On Wed, 30 Jul 2003, Hugh Wilson wrote:

> Hi all. I'm trying to add an external electric field to my
> simulations, and I'm assuming that the undocumented EXTERNAL POTENTIAL
> keyword will do what I want. From the code it seems that I have to specify
> the external potential in a binary file called extpot.unfo.grid, but it's not
> clear to me how I should lay this file out.
>
> There seem to be two READ statements - the second one which reads EXTPOT
> seems clear enough, but the first one which reads something called PSCR
> has me puzzled. It's also not clear to me how many entries I need to
> specify the potential (nr1*nr2s*nr3s, but I don't know what these mean)
> nor what units are used to specify the potential.
>
> If anyone knows how this section of the code works, I'd greatly appreciate
> some advice.
>
> Thanks,
>
> Hugh Wilson
> Nanoscale Simulation Laboratory
> School of Physics
> University of Sydney
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