[Wien] Poisson and clmsum

[Laurence Marks]

N.B., there can also be a discontinuity in the charge (small) due to the
tails of the core states which can be eliminated by doing "touch .lcore".

On Mon, Nov 21, 2016 at 8:36 AM, Laurence Marks <L-marks at northwestern.edu>
wrote:

> APW+lo methods have a step in the gradient of the density at the RMT. To
> avoid this use a lapw basis set: to reduce it increase RKMAX.
>
> ---
> Professor Laurence Marks
> "Research is to see what everybody else has seen, and to think what nobody
> else has thought", Albert Szent-Gyorgi
> http://www.numis.northwestern.edu
> Corrosion in 4D http://MURI4D.numis.northwestern.edu
> Partner of the CFW 100% gender equity project, www.cfw.org/100-percent
> Co-Editor, Acta Cryst A
>
>
> On Nov 21, 2016 07:39, "John Rundgren" <jru at kth.se> wrote:
>
>> Dear Peter Blaha and Gavin Abo,
>>
>> Non-overlapping muffin-tin spheres are used by WIEN2k and my LEED program
>> eeasisss (Elastic Electron-Atom Scattering in Solids and Surface Slabs).
>> But RMT(setrmt_lapw) is not automatically the best choice for
>> RMT(eeasisss). LEED touching radii of atoms depend on exchange-correlation
>> interaction between crystal electron gas (the WIEN2k electrons) and an
>> incident LEED electron (energy 20-500 eV).
>>
>> This is a N+1 electron scattering situation, where "N" signifies the
>> WIEN2k electrons and "1" an alien LEED electron.
>>
>> W2k can be reconciled with LEED using an atomic sphere approximation
>> (ASA) extending into the Fourier expansion realm of W2k. A while ago you
>> (P.B. and G.A.) suggested an ASA routine, in which I now use Poisson
>> differentiation of vcoul_ASA in order to obtain clmsum_ASA. I consider the
>> case LM=(0,0), sufficient for current LEED.
>>
>> The considered structure is a supercell = a surface slab 15 layers thick,
>> where layers 1-2 and 14-15 are C-O and O-C, respectively. Mirror symmetry
>> about layer 8. At the C-O layers vcoul_ASA(0,0) is continuous across the
>> RMT radius, but clmsum_ASA(0,0) versus radius shows a step of the order of
>> 10%.
>>
>> Is the step k-point dependent? It does not seem so. With 16 and 48
>> k-points the clmsum_ASA(0,0) steps are preserved within 6 digits.
>>
>> I shall be glad to supply the code. When the described numerical error is
>> fixed, WIEN2k and eeasisss can be re-run self-consistently within the model
>> of non-overlapping muffin-tin atoms.
>>
>> Regards,
>> John Rundgren
>>
>> KTH
>>
>>
>>
>>


-- 
Professor Laurence Marks
"Research is to see what everybody else has seen, and to think what nobody
else has thought", Albert Szent-Gyorgi
www.numis.northwestern.edu ; Corrosion in 4D: MURI4D.numis.northwestern.edu
Partner of the CFW 100% program for gender equity, www.cfw.org/100-percent
Co-Editor, Acta Cryst A
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