[Wien] mBJ potential and LDA+U

[Kamil Klier]

Dear Colleagues,

Please comment on the following question regarding the mBJ  
calculations (section 4.5.8 of the Wien2k 10.1 user manual):

Is it acceptable, on theoretical grounds, to calculate the scf cycle  
using LDA+U, not just LDA or PBE as stated in the User Manual, before  
the calculation using the mBJ potential?

This query is based on some calculations I have done for ZnO, and am  
now running for anion-doped ZnO.

I have read the PRL 2009 vol. 102 paper by Fabian Tran and Peter  
Blaha, and am getting a comparable bandgap for ZnO using Wien2k 10.1,  
as expected. The mBJ bandgap does not seem to depend on the functional  
in the scf calculation done in the first step (User Manual p. 49,  
section 4.5.8).
I have tried the 'regular' LDA, PBE, WC, -eece, and LDA+U and all of  
these yielded the same bandgaps.

However, the separation of the filled VB levels, O2p and Zn3d below  
it, was found significantly greater with LDA+U than by the other  
methods, appx. by 1 - 1.2 eV.  And this LDA+U result is in a better  
agreement with XPS experiment than the rest. So the 'best' result is  
obtained by LDA+U followed by mBJ.

If there are no conflicts between the potentials in LDA+U and mBJ, it  
would seem that this combination will yield better relative energies  
of the d-levels and the bandgap.  Please correct if this is wrong.

Greetings, Kamil Klier



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