[Wien] A question about RMT and AIM

[G.C.ZHOU]

 Dear Professor and users:
 I am doing the AIM calculation of ZnO, it has three structure:wurtzite,zinc-blende and rocksalt.
 when I do the calculation of BCP,the other setting are all same,I find RMT affect the result very greatly.
  
the structure is wurtzite,
   and set R(Zn)=1.75, R(O)=1.85, the Laplace of BCP is 5.003;
   when set R(Zn)=1.85, R(O)=1.90, the Laplace of BCP is 0.580,and the 
position of BCP is not correct.
  
the structure is zinc-blende,
  and set R(Zn)=1.75, R(O)=1.85, the Laplace of BCP is 4.993;
  when set R(Zn)=1.85, R(O)=1.90, I can't find the BCP.
  
the structure is rocksalt,
  and set R(Zn)=1.75, R(O)=1.85, the Laplace of BCP is 4.511;
  when set R(Zn)=1.94, R(O)=2.10, the Laplace of BCP is 3.256;
  
I am puzzled with this results, but the two results of evety structure are too different with only the RMT is changing. And the Laplace of rocksalt's BCP tells that, in the rocksalt structure, the covanlent of Zn-O bond turns more then wurtzite, it's contrary with our earlier cognition, which is the bonding became more ionic in this structure.
even worse, when I reduce the RMT, the laplace will turns smaller yet.

I set RKmax=9.0, LM=10, and set Ecut=-6.5Ry, there is no electron leak out.
and use x lapw -c to do the program.
  
Can tell me why the BCP change so much in different RMT, and which 
result should I take as the right one.
  
 Any advices is welcome!
  
Thanks.




G.C.ZHOU
2006-11-27
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