[Wien] mBJ + U

[Pablo de la Mora]

Dear Wien-users,
I have a system with a 4d and a 4f elements.
This system is an insulator, so my approach would be to use the mBJ 
potential.

The normal calculation gives a small gap with the 4f peak above but 
close to the gap.
Using the mBJ potential opens the gap considerably but moves the 4f peak 
into the gap and Ef is on the 4f peak. The calculation does not seem to 
converge. One could say that the system is an insulator since the the 4f 
orbitals are quite localized.
If I put the mBJ potential plus a Hubbard U then the gap remains the 
same, but the 4f peak moves down in energy outside the gap.
So, what is the correct solution? mBJ or 'mBJ + U'?

I have a further problem, I want to add spin-orbit coupling, but it 
seems to have problems with the mBJ potential.

     Yours

             Pablo