[Wien] charged and neutral cell

[pieper]

No, if you remove atoms in the case.struct file, you remove atoms, that 
is neutral entities. Just don't play around with the entry Z for the 
number of electrons (which you should not do if you are not sure what 
you are doing). It defaults to the nuclear charge - use the w2w2b 
interface and leave the entry empty in structgen, it will be filled in 
automatically. You need not do anything special during initialization to 
maintain charge neutrality.

As for the second question, readjust your concept of valence to align 
with how it is used within Wien2k. In a nutshell, distinction between 
core and valence electrons in Wien2k is made by their binding energy to 
a specific nuclear charge. If the binding energy is large enough, the 
total charge density of the electron is to high accuracy within the 
sphere of radius RMT around that nuclear charge - this is a core 
electron. If this is not the case, its a valence electron. It is much 
more difficult to be a core electron in Wien2k than it is in your 
classical thinking of Ba2+ and O2-. Leave that distinction to the 
program lstart during initialization. (There is a lot more, look into 
the introductory section of the UG and continue reading from there).

If you want to calculate defect structures, start from the perfect 
structure. Perhaps begin with examples that come with the 
Wien2k-package. After a successful scf run inspect the file case.scf. 
Search (grep) for
:NEC
You will find two numbers, the total number of charges, nuclear and 
electrons. They should be equal within the accuracy lstart uses to 
decide wether or not charge density leaks out of the RMT-sphere.

You will also find
:NOE
Which is the total number of not-core electrons, or

:CTOnnn
which is the total charge (in one spin channnel) in sphere nnn, and many 
other projections of the charge density on specific volumes, energy 
windows, spin or orbital states. Use the UG section on the scf file as 
an introduction. In adition you can use analysis programs like AIM (see 
UG, section on AIM) to calculate details.

Then create a new case directory and restart there by modifying your 
file case.struct - perhaps using programs like structgen and supercell.

Good luck



---
Dr. Martin Pieper
Karl-Franzens University
Institute of Physics
Universitätsplatz 5
A-8010 Graz
Austria
Tel.: +43-(0)316-380-8564


Am 30.11.2017 06:12, schrieb chin Sabsu:
> Dear Peter Sir and other experts,
> 
> Could you please explain how to deal charged vacancy and neutral
> vacancy?
> 
> If I remove an atom (say x^+2) from the unit cell then the Unit cell
> will be charged unit cell with charge -2e.
> If I remove an atom (say x^-2) from the unit cell then the Unit cell
> will be charged unit cell with charge +2e.
> 
> Are the above statements are correct?
> 
> If above statements are correct then please suggest me how to make the
> system neutral after creating vacancy.
> 
> Below are the lines from case.in2 and case.inm where, as far as I
> know, I need to  do some changes.
> 
> Assuming that I have xx NE in case.in2 and I remove an atom of vacancy
> +2 then how I should modify these two files so that the final
> defective cell remains charge neutral?
> 
> case.in2
> TOT             (TOT,FOR,QTL,EFG,FERMI)
>    -13.2    xx.0   0.50 0.05  1   EMIN, NE, ESEPERMIN, ESEPER0,
> iqtlsave
> 
> case.inm
> MSR1   0.0   YES  (BROYD/PRATT, BG charge (-1 for core hole), norm)
> 
> I have one another question:
> 
> How the number NE (here I kept it xx) in case.in2 changes case by
> case?
> 
> In case of BaZrO3 it, NE, is 40 but I could not find any way to
> calculate this number manually because Ba is having +2, Zr also +2 and
> O is -2. Total number of atoms are 5(Ba*1, Zr*1 and O*3) in the unit
> cell and below is electronic configuration of atoms.
> 
> Ba: _1s22s2_2p6_3s2_3p63d10_4s2_4p64d10_5S2_5P6_6S2_
> Zr: _1s22s2_2p6_3s2_3p63d10_4S2_4P6_4D25S2_
> _O:__1s2 2S2 2P4_
> 
> _Bold are treated as F (valence)  states during initialization._
> Looking forward to hearing from any of the expert.
> 
> Sincerely
> 
> Chin
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