[Pw_forum] quadrupole monents & GIPAW & a problem

[Zbigniew Lodziana]

Dear Davide,

  The structure is gamma (tetragonal symmetry) according to J. Chem. Phys. 44,
3348 (1966), all borons are tetrahedrally coordinated to oxygen. Convention is
ok. i think.


 There might be some confusion in the literature indeed. I will re-check for
other system ans report asap.

Thanks for help,

best regards,
Zibi


---------- Original Message -----------
From: Davide Ceresoli <davide.ceresoli at istm.cnr.it>
To: PWSCF Forum <pw_forum at pwscf.org>
Sent: Wed, 12 Sep 2012 10:32:11 +0200
Subject: Re: [Pw_forum] quadrupole monents & GIPAW & a problem

> Dear Zibi,
>      could you check with me whether your crystal is the gamma
> phase? experiments report Cq=0.042 MHz and eta=0.0 (Vorotilova,
> Dmitrieva and Samoson, 1987). B is an nearly cubic environment
> and the tetragonal symmetry should yield an axial tensor, hence
> vanishing eta.
> 
> Anyway, I recognize that B.pbe-tm-gipaw.UPF has some problems.
> It did work for NMR of small molecules, but I never tested it
> in solid state systems, I'm sorry.
> 
> The last thing to check, is the tensor convention. I think I'm
> using the Haeberlen convention, which is the same used by the
> Simpson code
> 
> (http://anorganik.uni-
> tuebingen.de/klaus/nmr/index.php?p=conventions/csa/csa).
> 
> HTH.
> 
> Best,
>      Davide
> 
> On 09/11/2012 06:00 PM, Zbigniew Lodziana wrote:
> > 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.
> >
> >
> 
> -- 
> +--------------------------------------------------------------+
>    Davide Ceresoli
>    CNR Institute of Molecular Science and Technology (CNR-ISTM)
>    c/o University of Milan, via Golgi 19, 20133 Milan, Italy
>    Email: davide.ceresoli at istm.cnr.it
>    Phone: +39-02-50314276, +39-347-1001570 (mobile)
>    Skype: dceresoli
> +--------------------------------------------------------------+
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------- End of Original Message -------