[QE-users] On-site Hubbard U for background orbitals

[William Hewett]

Hi all,

I'm interested in doing DFT+U calculations on the rare earth mono-nitride
GdN. The most successful calculations in the past have used multiple
Hubbard U terms (U_f and U_d) on the 4f and 5d electron channels on the Gd
ion. This has been done before using QE (Comput. Mater. Sci 95 (2014)
263-270).

I suspect that in v6.6 this may now be possible in the stable branch via an
onsite Hubbard V term on both the standard and background orbitals?

The pw.x input guide gives that Hubbard_V(na,na,k) will be the onsite
Hubbard interaction. After setting the appropriate values for the
background n, l and occupations of Gd in:

Modules/set_hubbard_l.f90
Modules/set_hubbard_n.f90
PW/src/tabd.f90

and increasing sc_size = 3 in Modules/parameters.f90

and compiling the code, I've used the following in the &SYSTEM block:

lda_plus_u=.true.
lda_plus_u_kind=2
Hubbard_V(1,1,1)=a
Hubbard_V(1,1,3)=b

I guess there will now be two Hubbard terms on that atom at side na, on the
standard and background orbitals.

However, I find the following error:

Error in routine init_lda_plus_u (1):
     lda_plus_u calculation but Hubbard_l not set

Any help is appreciated, I'm running QE 6.6 on Ubuntu 20.04.

Thanks

Will Hewett
Postdoctoral Researcher
Victoria University of Wellington
New Zealand
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