[QE-users] Transferred hyperfine coupling constants in TM-oxides

[Kris Harris]

Hi,

I'm starting out with QE and am attempting to learn by repeating some
literature results for hyperfine coupling constants for Li in Li2MnO3.

Capsoni et. al in 1997 Phys. Rev. B. list the experimental value for A as
4.31 MHz for one site (there are 2 other sites at essentially half that A)

Mali. et al. were able to reproduce that value very well in Chem. Comm. in
2010 (DOI:10.1039/c003065a) using QE with the GIPAW module.  I'm attempting
to reproduce that result, following their method as close as possible.

I used dist.x to attempt to verify the structure, and did some convergence
tests with respect to ecutwfc and k-points to make sure the calculations
was reasonable. I also verified that the binary I have reproduced the H2O+
test case included in the distribution.

The result I get is quite a long ways off (0.06 MHz and -7 MHz instead of
~4.3 and ~2.15 MHz).

Any help on what I've managed to do wrong here would be greatly appreciated.


*Input and relevant output below:*

My scf input file (I swapped the *b* and *c* axes from the standard setting
of the C2/m space group to use QE's convention for the unit cell face that
has the extra lattice point in this non-primitive lattice):

 &CONTROL
                 calculation = 'scf' ,
                restart_mode = 'from_scratch' ,
                      outdir = './scratch/' ,
                  pseudo_dir = './pseudo/' ,
                      prefix = 'Li2MnO3' ,
                   verbosity = 'high' ,
 /
 &SYSTEM
                       ibrav = 13,
                 space_group = 12,
                           A = 4.929200 ,
                           C = 8.531500 ,
                           B = 5.025100 ,
                       cosAC = 0 ,
                       cosAB = -0.33315 ,
                       cosBC = 0 ,
                         nat = 6,
                        ntyp = 3,
                     ecutwfc = 120.0 ,
                 occupations = 'smearing' ,
                     degauss = 0.02 ,
                    smearing = 'gaussian' ,
                       nspin = 2 ,
   starting_magnetization(2) = 0.7,
  /
 &ELECTRONS
                    conv_thr = 1.0d-8 ,
                 mixing_mode = 'plain' ,
                 mixing_beta = 0.7 ,
             diagonalization = 'david' ,
 /
ATOMIC_SPECIES
   Li    6.94100  Li.pbe-tm-gipaw-dc.upf
   Mn   54.93800  Mn.pbe-rrkj-semi-gipaw-dc.upf
    O   15.99900  O.pbe-tm-new-gipaw-dc.upf
ATOMIC_POSITIONS crystal_sg
ATOMIC_POSITIONS crystal_sg
Li       0.00     0.00     0.50
Li       0.00     0.50     0.00
Li       0.00     0.50     0.6606
Mn       0.00     0.00     0.16708
O        0.2189   0.2273   0.00
O        0.2540   0.2233   0.32119
K_POINTS automatic
  4 4 4  1 1 1

gipaw input:

&inputgipaw
        job = 'hyperfine'
        prefix = 'Li2MnO3'
        tmp_dir = './scratch/'
        spline_ps = .true.
        verbosity = 'high'
        hfi_output_unit = 'MHz'
        hfi_nuclear_g_factor(1) = 2.170951
/

The fermi-contact output is:
     ----- Fermi contact in MHz -----
               bare            GIPAW           core-relax      total
     Li   1      -15.412717       18.246446       -2.771682        0.062047
     Li   2      -15.450597        9.404951       -0.969447       -7.015093
     Li   3      -15.451374        9.237472       -0.964451       -7.178353
     Li   4      -15.451374        9.237473       -0.964451       -7.178352

-Kris Harris
Research Associate
McMaster University
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