[Pw_forum] Too large susceptibility in NMR/ g-tensor calculations using GIPAW
Davide Ceresoli
davide.ceresoli at materials.ox.ac.uk
Sun Oct 17 14:52:20 CEST 2010
On 10/17/2010 11:46 AM, Aurab wrote:
> Dear QE users and developers,
> I am facing a strange problem calculating g tensor of Al doped ZnO
> systems. Some elements of the susceptibility tensor (chi_bare) is
> printed as ****** . I assume this is probably due to occurrence of a
> very large number for that element. Could you please tell me why the
> susceptibility is blowing up and also what is chi_bare pGv and chi_bare
> vGv. The block of the output file is given below.
>
>
>
> End of magnetic susceptibility calculation
>
> f-sum rule:
> -285.026632 1.736420 0.008960
> 1.735646 -277.370374 0.014146
> 0.008277 0.011673 -280.653668
>
> f-sum rule (symmetrized):
> -281.198503 0.000000 0.000000
> 0.000000 -281.198503 0.000000
> 0.000000 0.000000 -280.653668
Dear Aurab,
it would be useful if you could post your input files.
In the meanwhile I can only guess: is your cell hexagonal?
GIPAW is incompatible with symmetries that do not map cartesian
axis on themselves. Try nosym = .true.
How many electrons do you have? the f-sum rule is a good indicator
of the convergence of GIPAW calculations. In my experience,
the % error on chemical shift is similar to the % error on the
f-sum rule, but the error on susceptibilities is much larger.
Is your system spin-polarized?
To converge the f-sum rule, you must increase the number of
k-points.
HTH.
Cheers,
Davide
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