[Wien] XPS core binding energy

[Peter Blaha]

I don't know what you are doing wrongly.

I just did a "lousy" calc. using a 3x3x1 cell with Slaters transition 
state and got -290.2 eV.

This is not great, but probably still reasonable. Note: this value is 
without convergence checks of cell-size, k-mesh,... and might not be 
accurate.

Did you check   :NEC01    for charge neutrality ? Maybe you put the 
wrong sign in case.inm ?


On 07/27/2017 07:14 AM, Alexey Kartsev wrote:
> Dear WIEN2K users.
>
> My project involves XPS study of adsorbed molecules on the surface of
> graphene.
> As a starting point, I have tried to calculate binding energy for a 1S
> core state of pristine graphene but I did not succeed. The value 296.8
> eV I have got is too far from the experimental results 284.5 eV.
> Currently, I am using 16.1 version of WIEN2K.
> In my calculations, I have used R*Kmax=7 and 6x6x1 k-points mesh, so it
> is should be a fairly good numbers. I have tried to increase another
> parameter Gmax from the 12 to 14 but the result is more or less the same.
>
> Basically, from the WIEN2K forum and presentation slides, I understood
> that delta-SCF method should be quite precise. It claimed that by using
> WIEN2K it is possible to reproduce experimental values for TiC, Ti4C4
> and TiN within error less than 1%.
>
> The procedure I have followed in order to calculate core binding energy
> is following:
> 1)Create large enough supercell in order to avoid hole-hole interaction.
> 2)To do an SCF calculation for a ground state of that supercell where I
> can grab a total energy Eg for the ground state.
> 3)Choose one single atom in the supercell to be perturbed (ionised)
> which correspond to the element of interest.
> 4) Take away one electron from the core state you want to study in that
> atom by changing an occupation number in the case.inc. In the pristine
> graphene case, it is the 1S state in one of the supercell atoms. So for
> graphene, you have to change occupation of 1S orbital from the 2 to 1.
> 5)Then in order to enforce charge neutrality of the supercell, you
> should put BG charge equal -1 in the case.inm file.
> 6)Do an SCF calculation for an excited system which will give you a
> value of total energy for the ionised supercell - Eexc.
>
> So, in principle, the difference Eb=Eg-Eexc should give me the XPS shift
> for the chosen core state. And if your supercell is big enough the
> results should be close to the experimental value.
>
> Here are some results for few different parameters and supercells:
> 4x4 supercell R*Kmax=7 Gmax=14
> k-points 4x4x1 dE=296.787287946 eV
> k-points 6x6x1 dE=296.87888205 eV
>
> 3x3 supercell R*Kmax=7 Gmax=12
> k-points 6x6x1 dE=298.147365363 eV
> R*Kmax=6 k-points 3x3x1 dE=297.998728554
> R*Kmax=5 k-points 3x3x1 dE=298.51212406
>
> 5x5 supercell R*Kmax=7 Gmax=12
> k-points 4x4x1 dE=297.039874874
>
> Talking about Slater transition method - it gives me an even worse number.
> So, I took 3x3 super cell with a 1/2 core-hole.
> The 1s level energy of perturbed C atom is  -25.266283216 Ryd. Fermi
> energy is -0.5810770100 Ryd.
> So Eb= -24.6852062060=335.859462333 eV - very bad.
>
> Am I doing something wrong or misunderstanding something?
> Could it be a problem with WIEN2K compilation?
> I have tried to calculate DOS and charge density for a pristine graphene
> and they look reasonable.
>
> ==============================================
> *With best regards, *
> *   Kartsev Alexey.*
>
> Postdoc Fellow
> Atomistic Simulation Centre,
> School of Mathematics and Physics,
> Queen's University Belfast,
> Belfast BT7 1NN, Northern Ireland,
> United Kingdom
> E-mail: _A.Kartsev at qub.ac.uk <mailto:A.Kartsev at qub.ac.uk>_
>
>
>
>
>
>
>
> <https://mailtrack.io/> Sent with Mailtrack
> <https://mailtrack.io/install?source=signature&lang=en&referral=karec1@gmail.com&idSignature=22>
>
>
>
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
> SEARCH the MAILING-LIST at:  http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
>

-- 

                                       P.Blaha
--------------------------------------------------------------------------
Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
Email: blaha at theochem.tuwien.ac.at    WIEN2k: http://www.wien2k.at
WWW:   http://www.imc.tuwien.ac.at/TC_Blaha
--------------------------------------------------------------------------