[ase-users] about charged slab calculation

[John Kitchin]

maybe you could use something like this:

http://gilgamesh.cheme.cmu.edu/jacapo/jacapo/3-surfaces/3.9-external-potential/3.9.0-external-potentials.html

to setup an external dipole field that decouples the cells.?


in the old ASE2 code there was this possibility.

SetElectrostaticDecoupling(numberofgaussians=3,ecutoff=100):
    Add electrostatic decoupling (Jan Rossmeisl). Decoupling activates
the three dimensional electrostatic decoupling. Based on paper by
Peter E. Bloechl: JCP 103 page7422 (1995).

I don't think this is currently implemented in Jacapo, but it could be
done. you just need to setup the right netcdf variables to tell the
fortran code what to do i think.

j


John

-----------------------------------
John Kitchin
Assistant Professor
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803
http://kitchingroup.cheme.cmu.edu





On Wed, Feb 23, 2011 at 10:58 PM, Duy Le <ttduyle at gmail.com> wrote:
> It is not about the code. It is about theory. Do you know any theory
> that helps you correct the total energy of the charge system whose
> supercell is NOT Cubic (needed for slab model)?
>
> --------------------------------------------------
> Duy Le
> PhD Student
> Department of Physics
> University of Central Florida.
>
> "Men don't need hand to do things"
>
>
>
> On Wed, Feb 23, 2011 at 10:33 PM, Huang Bing <hbdft2008 at gmail.com> wrote:
>> They say that it's not possible to do charged slab calculation in vasp,
>> so i wonder if these kind of calculation is valid or not in Dacapo.
>> see this url
>> http://cms.mpi.univie.ac.at/vasp-forum/forum_viewtopic.php?4.2463
>> for detail, or have a look at the text below, which is copied directly
>> from the contents in that link:
>>>I have a question. Is it possible to optimize charged unit cell, for
>>> example,
>>>if I want to investigate adsorption of charged species on neutral surface?
>>>If yes, where can I read about method, possible errors, etc?
>>>Thank you in advance.
>> Here is the admin's reply:
>> a) on charged systems in general, please have a look in the manual
>>     (chapter multipole corrections)
>> b) Actually, you MUST NOT set the number of electrons manually for
>>     a slab calculation. I.e., when you calculate the surface+adsorbate
>>    system, you are not allowed to select a specific charge state for the
>>    adsorbate by increasing the number of electrons manually. Specific
>>    charge state calculations make sense only in 3d systems and for
>>    cluster calculations.  The electrostatic energy of such a slab is
>>     however only conditionally convergent and in practice even infinite
>>     (BASIC, BASIC ELECTROSTATICS).
>>    Only if the calcuations are done properly, i.e., if your slab is large
>>    enough and the lateral dimension (x,y) of your surface is large enough
>>     (test for the necessary 2D dimension, the total energy has to converge
>>     to the correct value with (1/(distance between the charged species) )
>>    the energy should converge to the proper value, i.e. the adsorbed species
>>  should acquire the correct charge state (then, it is acquired
>> automatically).
>> Any comments is highly appreciated!
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>