[Wien] electrostatic potentials

[Laurence Marks]

You cannot do this via a simple fft, but can use lapw3 then the Mott
formula. This has already been done, and (predictably) the difference
between neutral atom scattering factors from Doyle-Turner, tabulated
x-ray and dstart are very small, much less than the difference
compared to a solid. See Acta Crystallographica Section A 62: p.
208-216, 2006


On Mon, Apr 6, 2009 at 5:14 AM, Peter Blaha
<pblaha at theochem.tuwien.ac.at> wrote:
> I don't know what you have made wrong, but I don't believe that.
>
> You know that the potential will be in Ry (not Hartree !), which makes
> a factor of two!
>
> PS: An atom in a supercell you would always do with just ONE k-point
> You also have to make sure you are calculating/comparing the right thing.
> Many atoms need spin-polarization! and in GGA you may obtain a
> "non-spherical" atom (at least when you break cubic symmetry);
> i.e. in carbon two 2p-orbitals (with spin-up) might be fully occupied
> while the 3rd one is empty,.... leading to non-spherical potentials
> (visible further away from the nucleus).
>
> simon.kurasch at uni-ulm.de schrieb:
>> Dear Wien2k users,
>>
>> I want to work with the coulomb-potentials created by Wien2k out of
>> the file case.vcoul.
>> For comparison with potentials from isolated atom models (like Doyle
>> Turner or potentials by Kirkland) I put one atom (C or Ag) into a 10
>> ANG primitive cell and run SCF using gga -6Ry, about 200 K-points (I
>> also performed calculations with 1000K) and krmax 7. Afterwards I used
>> lapw5 to create linescans of vcoul. lapw5.def and case.in5 are shown
>> below.
>>
>> There are big deviations: in the range of 0.1-0.3 Ang from the core
>> the Wien2k potential is about a factor of 2 smaller and from 0.6-1.5
>> Ang the Wien2k potential is a factor of 2 larger.
>>
>> One idea is to calculate the electrostatic potential form the Wien2k
>> charge density clmsum via Mott equation. Has anyone experience with
>> using this equation? I already tried to implement it using fftw3 but I
>> didn't succeed.
>> There's probably already software available to performe these
>> calculations, but I was not able to find it yet.
>>
>> I would be very grateful for some help.
>> Simon Kurasch
>>
>>
>> lapw5.def
>> 5 ,'Single_Ag.in5', 'old',    'formatted',0
>> 6 ,'Single_Ag.output5',   'unknown','formatted',0
>> 8 ,'Single_Ag.struct',    'old',    'formatted',0
>> 9 ,'Single_Ag.vcoul',    'old',    'formatted',0
>> 10,'Single_Ag.tmp',       'unknown','unformatted',0
>> 11,'Single_Ag.vcouldn',  'unknown','formatted',0
>> 12,'Single_Ag.sigma',     'unknown','formatted',0
>> 20,'Single_Ag.rho_onedim','unknown','formatted',0
>> 21,'Single_Ag.rho',       'unknown','formatted',0
>>
>> case.in5
>> 1  1  1  2
>> 2  2  1  2
>> 2  2  1  2
>> 3  3  3
>> 500   1
>> RHO
>> ATU VAL NODEBUG
>> NONORTHO
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>
> --
>
>                                       P.Blaha
> --------------------------------------------------------------------------
> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
> Email: blaha at theochem.tuwien.ac.at    WWW: http://info.tuwien.ac.at/theochem/
> --------------------------------------------------------------------------
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>



-- 
Laurence Marks
Department of Materials Science and Engineering
MSE Rm 2036 Cook Hall
2220 N Campus Drive
Northwestern University
Evanston, IL 60208, USA
Tel: (847) 491-3996 Fax: (847) 491-7820
email: L-marks at northwestern dot edu
Web: www.numis.northwestern.edu
Chair, Commission on Electron Crystallography of IUCR
www.numis.northwestern.edu/
Electron crystallography is the branch of science that uses electron
scattering to study the structure of matter.