[ase-users] about charged slab calculation

[Duy Le]

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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