[Pw_forum] quadrupole monents & GIPAW & a problem

[Zbigniew Lodziana]

Dear users & developers,

While calculating quadrupole moments with GIPAW I have experienced a strange
output that confuses me and it is difficult for interpretation, at least to me.

Performing calculations for LiBO2 (with occupancies = fixed!) efg calculations
provide for Boron:
(a)	Cq=   0.0208 MHz    eta= 0.00000
(b)	Cq=   2.0747 MHz    eta= 0.00000
(c)	Cq=   0.0228 MHz    eta= 0.00000

Where 
(a) is with TM potential
[https://sites.google.com/site/dceresoli/pseudopotentials/B.pbe-tm-new-gipaw-dc.UPF?attredirects=0];

(b) also TM
[https://sites.google.com/site/dceresoli/pseudopotentials/B.pbe-tm-gipaw.UPF?attredirects=0];

(c) with ultrasoft.

Experimental value is Cq=2.56, eta=0.6; theoretical report Cq=2.552, eta=0.54

Test calculations with other more accurate potentials unfortunately do not
solve problem.

And the problem is that the worst description of the valence states provides
(at least numerically) best Cq; besides it is difficult to understand how
small changes in the valence state might result in so large – two orders of
magnitude – changes in the core region. For other systems changes are even 3
orders.

Structural parameters are reasonable.

For oxygen I did not found such a large variations, for Al Cq is reasonable.

Does anyone experienced similar problems or has any hint where the problem
could origin form?

Thank you in advance,
Best regards,

Zibi


Pw.x – 5.0
Gipaw.x 5.0
(version 4.3a gives similar results)
-----------------------------------
Pw.x

&control
    calculation = 'scf'
    prefix = 'LiBO2'
    restart_mode = 'from_scratch'
    pseudo_dir = './pseudo/'
    outdir = './tmp/'
    verbosity = 'high'
    wf_collect=.true.
/
&system
    ibrav = 0
    celldm(1) = 1.0
    nat = 16
    ntyp = 3
    ecutwfc = 110
    ecutrho = 1000
    spline_ps = .true.
    occupations  =  'fixed' 
/
&electrons
    diagonalization = 'david'
    diago_thr_init = 1e-4
    mixing_mode = 'plain'
    mixing_beta = 0.1
    conv_thr =  1e-10
/

ATOMIC_SPECIES
Li 6.941  Li.pbe-tm-gipaw-dc.UPF
B  10.811 B.pbe-tm-gipaw.UPF
O  15.999 O.pbe-tm-new-gipaw-dc.UPF

CELL_PARAMETERS (alat=  1.00000000)
   8.020588949   0.000000000   0.000000000
   0.000000000   8.020588949   0.000000000
   0.000000000   0.000000000  12.497695405

ATOMIC_POSITIONS (crystal)
Li       0.000000000   0.000000000   0.500000000
Li       0.500000000   0.000000000   0.249999998
Li       0.500000000   0.500000000   0.000000000
Li       0.000000000   0.500000000   0.750000002
B        0.000000000   0.000000000   0.000000000
B        0.500000000   0.000000000   0.750000000
B        0.500000000   0.500000000   0.500000000
B        0.000000000   0.500000000   0.250000000
O        0.154649384   0.249987860   0.125014658
O        0.845350616   0.750012140   0.125014658
O        0.249987860   0.845350616   0.874985342
O        0.750012140   0.154649384   0.874985342
O        0.345350616   0.250012141   0.625014658
O        0.654649384   0.749987859   0.625014658
O        0.749987859   0.345350616   0.374985342
O        0.250012141   0.654649384   0.374985342

K_POINTS automatic
4 4 4   1 1 1
------------------------------------------
Gipaw.x

&inputgipaw
        job = 'efg'
        prefix = 'LiBO2'
        tmp_dir = './tmp/'
        iverbosity = 11
        spline_ps = .true.
        Q_efg(1) = 4.06    ! 7Li
        Q_efg(2) = 4.06    ! 11B
        Q_efg(3) = 2.55    ! 17O
!       q_gipaw    = 0.01
/ 
Q_efg for Li might not be perfect but shall not matter.