[Wien] Are fractionally charged atoms possible in Wien2k?

[Oleg Rubel]

Dear Wien2k Users,

in calculations of polar semiconductor surfaces, I came to the point where 
I need to introduce fractionally charged hydrogen atoms in order to 
passivate an irrelevant side of the slab. The fractionally charged atom 
means an atom with a non-integer nuclear charge and the corresponding 
non-integer number of electrons, i.e., 1.25 or 0.75 in the case of 
fractionally charged hydrogen atoms.

My first attempt with WIEN2k_08.1 (Release 14/12/2007) was not successful. 
I edited the structure file using w2web and put Z=0.75 instead of default 
1.0 for hydrogen. In the structure file, I have got 0.8 instead of 0.75, 
which is a fault of w2web because Z has F5.2 format. Of course it is not 
what I want, but I decided to stay with 0.8 and continue further. Real 
problems begin with LSTART. I edited the case.inst file in order to bring 
the number of electrons in agreement with the nuclear charge Z=0.8. The 
corresponding part of case.inst is shown below:

H 1
1
1,-1,0.7  N
1,-1,0.1  N

LSTART stops on 1S orbital of the pseudohydrogen and generates the 
following error message:

ERROR !!! nstop,iter,tets,test 28 1 9.999999939225290E-009

If I put the hydrogen charge back to Z=1 and correspondingly change the 
case.inst file, LSTART runs error free.


Any ideas?


Thank you in advance,

Oleg Rubel

===========================
Oleg Rubel, Ph.D.
Faculty of Physics
Philipps University Marburg
Renthof 5, 35032 Marburg, Germany
E-mail: Oleg.Rubel at physik.uni-marburg.de
Homepage: http://www.staff.uni-marburg.de/~rubel/