[Wien] BaTiO3.vcoul

[John Rundgren]

Dear Dr Blaha,
Thank you for the factor 1/sqrt(4pi). My calculation reproduces the atomic charges with excellent accuracy, just as you say. It is most encouraging to see such a test.
Best regards,
John
John Rundgren
Department of Theoretical Physics, Royal Institute of Technology (KTH),
AlbaNova University Center, SE-10691 Stockholm, Sweden
fax +46 8 5537 8216, voice +46 8 5537 8171,
home page http://www.theophys.kth.se/~jru
________________________________________
From: wien-bounces at zeus.theochem.tuwien.ac.at [wien-bounces at zeus.theochem.tuwien.ac.at] On Behalf Of Peter Blaha [pblaha at theochem.tuwien.ac.at]
Sent: Monday, September 14, 2009 3:52 PM
To: A Mailing list for WIEN2k users
Subject: Re: [Wien] BaTiO3.vcoul

I don't quite understand where the problems are and where your numbers come from ???

The file case.vsp    contains already R*V-total .
For a Ti atom  its first value is -0.440393833562E+02     (close to 2 * 22
or for Oxygen it is:              -0.161255917246E+02               2 * 8

In case.vcoul    the  radial expansion coeff. of  R**2 * V-coul are stored.
The expansion reads (in a simplified form)    r**2 * V = sum(LM) V_LM(r) Y_LM
This means, you have to multiply with a spherical harmonics Y_00, which is 1/sqrt(4pi)

So to obtain R*V :
for Ti the first value in case.vcoul is: -0.779715438164E-02;
         since R0=0.00005000, you have to divide by R0 and divide by sqrt(4 pi). this gives   43.99
         which is not bad after all .....

How did you produce your numbers ?

In any case, copy case.vcoul to case.clmval and use    x lapw5   to produce the coulomb-pot in
real space along a line or in a plane.


John Rundgren schrieb:
> Dear All,
> With option R2V in BaTiO3.in0, BaTiO3.vcoul is written out. It is interesting to compare the files
>
> radius times BaTiO3.vsp
> radius squared times BaTiO3.vcoul (spherical part)
>
> The files start with the values given in the Table below:
>
> Atom    Z    r*vsp    r*vcoul
> Ba      56   -111.3   -400.8
> Ti        22   -43.0    -157.8
> O         8    -15.6    - 60.4
>
> As User's Guide 4.2 says, vsp is in units of Rydbergs and r*vsp is approximately -2*Z. But what units and what approximation are used for r*vcoul ? User's Guide and the comments of file BaTiO3.vcoul are silent on this point.
>
> I had expected that r*vcoul/Z would be v_e_r_y close to an integer. Isn't it true that the centre of an atom is the same whether the atom is free or situated in a crystal ?
> Best regards,
> John
>
> John Rundgren
> Department of Theoretical Physics, Royal Institute of Technology (KTH),
> AlbaNova University Center, SE-10691 Stockholm, Sweden
> fax +46 8 5537 8216, voice +46 8 5537 8171,
> home page http://www.theophys.kth.se/~jru
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien

--

                                       P.Blaha
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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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