[Pw_forum] scf convergence of defected hBN

[Paolo Giannozzi]

You should add a smearing, even if you think that your system is not
metallic (if you think it is, you MUST add a smearing). Something like
occupations='smearing', smearing='gaussian', degauss=0.01 to 0.05 or so.
You might also try a spin-polarized calculation.

Paolo

On Wed, Dec 27, 2017 at 3:51 AM, lt15 <lt15 at rice.edu> wrote:

>
> Hi
>
> I was doing a 'scf' calculation for a defected h-BN structure as shown in
> the attached figures. I would like to obtain the charge density of the
> layer especially around the defect. But I found the calculation couldn't
> converge as the 'estimated scf accuracy' in the output file keeps
> fluctuating. In the input file, I tested different mixing_mode like 'plain'
> and 'local-TF'. or the mixing_beta value like 0.01. 0.1, 0.3, 0.7. But
> still, it didn't converge even after 8 hours running. In structure in-a,
> the defected boron atom was far away from its original lattice position, as
> shown in in-a.png. In structure in-b, the defected boron atom plus a
> nitrogen atom around the edge of layer were deleted, as shown in in-b.png.
> In structure in-b, the layer still maintained neutral electricity and kept
> the void defect in the center. However, neither structure can converge.
> Could you give some suggestions about the convergence issue for this
> defected structure? Thank you.
>
> best,
> Lei
>
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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