Dear Members,
I have been working with LiCoO2 and CoO2, performing DFT calculation to
determine the intercalation potential. However, when it comes to CoO2 after
adding the Hubbard correction (DFT+U) convergences cannot be reached. I have
just added two lines to the original input file: lda_plus_u = .true. and
Hubbard_U(1) = 3.4 (this value I took from a paper: Aykol, M., Kim, S., &
Wolverton, C. (2015). Van der Waals interactions in layered lithium cobalt
oxides. The Journal of Physical Chemistry C, 119(33), 19053-19058.). I have
performed all the calculations using QE v.6.7MaX.
Kindly have a look at the input file and suggest why its so hard to converge
this relatively simple system after adding the U correction
&CONTROL
calculation = 'scf'
outdir='tmp',
prefix = 'CoO_U'
pseudo_dir = '.',
tprnfor = .true.
verbosity = 'high'
/
&SYSTEM
ecutrho = 800
ecutwfc = 70
ibrav = 0
nat = 3
ntyp = 2
occupations='smearing', smearing='gauss', degauss=0.015,
nspin=2
starting_magnetization(1) = 0.1
lda_plus_u = .true.,
Hubbard_U(1) = 3.4
vdw_corr='grimme-d3'
/
&ELECTRONS
/
ATOMIC_SPECIES
Co 58.933194 co_pbe_v1.2.uspp.F.UPF
O 15.999 o_pbe_v1.2.uspp.F.UPF
CELL_PARAMETERS angstrom
2.8413505554 0.0000000000 0.0000000000
1.4206751885 2.4606823642 0.0000000000
1.4206754552 0.8202267469 4.7143528794
ATOMIC_POSITIONS crystal
Co 0.0000000000 0.0000000000 0.0000000000
O 0.7396634820 0.7396634820 0.7810095550
O 0.2603365180 0.2603365180 0.2189904750
K_POINTS automatic
6 6 6 0 0 0
I had already tried to change the conv_thr, diagonalization, etc. as it is
show below
conv_thr = 1e-5
diagonalization = 'cg'
mixing_beta = 0.3
mixing_mode = 'local-TF'
But noting seems to work. I believe that the problem could be related to the
magnetization (hing and low spin state). Maybe to force the system to low spin
state but I not sure how to do that or if the problem is connected with that.
Additionally, I use gbrv pseudopotential for these calculation.
Best regards
William Pancho
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