[Wien] XPS is there a shift of fermi energy from core-hole? Can I estimate it?
Laurence Marks
L-marks at northwestern.edu
Mon Apr 13 21:26:19 CEST 2015
It looks like you do not have any really deep cores available.
Beyond Peter's comment, if you look in case.output0000 there may be a line
" v-mean, v0,u0 (1.852427509440732E-002,-5.478545357123084E-019)
(6.233636072145684E-003,-5.478545357123084E-019)
(50.4652036532662,0.000000000000000E+000)
(-1.229063902226163E-002,0.000000000000000E+000)"
Peter sometimes comments it out, I often comment it back in. This will
tell you what absolute offset has been used, i.e. how much the
potential in the PW's has been shifted which is what you need. You
would need to do a little digging in the code to find out exactly what
the units are; I did it once and it worked but I have forgotten,
(Peter may know.) It's a little tricky as the relevant code uses odd
variable names,
N.B., note to self and/or Peter: it would be nice to have this
properly output in the "right" units.
On Mon, Apr 13, 2015 at 1:37 PM, David Olmsted <olmsted at berkeley.edu> wrote:
> Laurence,
> Thank you for the suggestion. It makes sense, but it may not work here.
> For the 48 atom supercell of AlPO4, excluding the two P atoms that are
> second neighbors of the Al with the half core-hole, the difference in the
> P-1s energy between the run with and without the half core-hole range from
> 0.43 eV to 0.55 eV for the various atoms. On the other hand, excluding the
> atom with the core-hole, the difference for Al-1s energy between the two
> runs varies from -0.02 to 0.12 eV. (The Al-1s is at about -110 Ry, and the
> P-1s at about -150 Ry.) So the different deep core levels disagree too
> much.
>
> Best,
> David
>
> -----Original Message-----
> From: wien-bounces at zeus.theochem.tuwien.ac.at
> [mailto:wien-bounces at zeus.theochem.tuwien.ac.at] On Behalf Of Laurence Marks
> Sent: Monday, April 13, 2015 9:36 AM
> To: A Mailing list for WIEN2k users
> Subject: Re: [Wien] XPS is there a shift of fermi energy from core-hole? Can
> I estimate it?
>
> A comment that may be useful. If you have a deep core level on another atom
> that is not that close you may be able to use that as a reference instead --
> seemed reasonable when I used it in the past for something else.
>
> On Mon, Apr 13, 2015 at 11:04 AM, David Olmsted <olmsted at berkeley.edu>
> wrote:
>> Dear Peter and all list members,
>> [Peter, thanks again for the response below.]
>>
>> I am modeling XPS binding energy using a one-half core-hole, offset
>> by background charge.
>> I am looking at the Al-2p states in the Al-P-O-H system, and looking
>> at shifts in the XPS energy between hydrated and non-hydrated
>> structures. This is for comparison with experimental work.
>>
>> Is there a shift in the Fermi energy because of the missing 1/2
> electron?
>> (I believe Laurence Marks made a general mention of worrying about
>> Fermi energy shifts when doing XPS in this mailing list.) Since I
>> have a finite sized computational cell, it seems like reducing the
>> number of electrons should reduce the Fermi energy a bit, compared to
>> a larger cell. Is this is so, is there some way I can estimate it,
>> either just to see if it is significant, or perhaps even to correct for
> it?
>>
>> Apparently I cannot compare the Fermi energy of different runs, each
>> with one-half of a core-hole but different numbers of atoms, because
>> of the issue of the zero of energy that Peter Blaha points out below.
>>
>> Thanks,
>> David
>>
>> David Olmsted
>> Assistant Research Engineer
>> Materials Science and Engineering
>> 210 Hearst Memorial Mining Building
>> University of California
>> Berkeley, CA 94720-1760
>>
>> -----Original Message-----
>> From: wien-bounces at zeus.theochem.tuwien.ac.at
>> [mailto:wien-bounces at zeus.theochem.tuwien.ac.at] On Behalf Of Peter
>> Blaha
>> Sent: Friday, April 10, 2015 1:24 PM
>> To: A Mailing list for WIEN2k users
>> Subject: Re: [Wien] Which fermi energy for XPS?
>>
>> No, I don't think so.
>>
>> Every calculation uses its own Energy-zero (the average of the
>> Coulomb-potential in the interstitial region is set to zero), so
>> clearly one must use EF and E-2p from the same (half-core hole)
> calculation.
>>
>> Eventually, you can check the k-mesh, as with a small k-mesh, EF could
>> vary a bit.
>> (I hope you have used "comparable k-meshes". This means the mesh for
>> the
>> 2x2x1 supercell should be by by a factor of two smaller in x,y than
>> for the primitive cell
>> (eg. 2x2x2 vs 4x4x2)
>>
>> Am 10.04.2015 um 19:33 schrieb David Olmsted:
>>> I am modeling XPS binding energy using a half core-hole, offset by
>>> background charge. As I understand the method that has been
>>> explained here recently, one computes the binding energy as the
>>> energy of the state from case.scfc minus the Fermi energy from ':FER' in
> case.scf.
>>> Should the Fermi energy be for the configuration with the half
>>> core-hole, or a configuration without the core-hole? As explained
>>> below, from my results it looks as if it should be the same
>>> configuration,
>> but without the core hole.
>>>
>>> Some details:
>>> Version 14.2
>>> I am computing the differences in the XPS binding energy for Al-2p
>>> for cyrstals in the Al-P-O-H system to see how the binding energy
>>> changes between hydrated and non-hydrated configurations. This is
>>> for comparison with experimental results. (The actual material is
>>> amorphous, but I am hoping the effects of on the spectra will be at
>>> least qualitatively
>>> similar.)
>>>
>>> The simplest structure is AlPO4, berlinite. I have run two
>>> configurations, the primitive cell with 18 atoms, including 3 Al
>>> atoms, and a 2x2x1 supercell. In each case I have made one Al
>>> unique, then added one-half core-hole in case.inc and offset it with
>>> -0.5
>> background charge in case.inm.
>>> For simplicity I will show the results just for the triplet state.
>>> Lines are from case.scf and case.scfc.
>>>
>>> -------- 2x2x1 supercell, no core-hole
>>> :LABEL4: using the command: run_lapw -ec 0.00001 -p <skip>
>>> :FER : F E R M I - ENERGY(TETRAH.M.)= 0.0547409802
>>> :NEC01: NUCLEAR AND ELECTRONIC CHARGE 720.00000 720.00112
>>> :NEC02: NUCLEAR AND ELECTRONIC CHARGE 720.00000 720.00000
>>> :NEC03: NUCLEAR AND ELECTRONIC CHARGE 720.00000 720.00000
>>>
>>> -------- primitive cell, no core-hole
>>> :LABEL4: using the command: run_lapw -ec 0.00001 -p -NI <skip>
>>> :FER : F E R M I - ENERGY(TETRAH.M.)= 0.0564539224
>>> :NEC01: NUCLEAR AND ELECTRONIC CHARGE 180.00000 180.00073
>>> :NEC02: NUCLEAR AND ELECTRONIC CHARGE 180.00000 180.00000
>>> :NEC03: NUCLEAR AND ELECTRONIC CHARGE 180.00000 180.00000
>>>
>>> -------- 2x2x1 supercell, half core-hole
>>> :LABEL4: using the command: run_lapw -ec 0.00001 -p <skip>
>>> :WARN : CHARGED CELL with -0.500
>>> :FER : F E R M I - ENERGY(TETRAH.M.)= 0.0609755546
>>> :NEC01: NUCLEAR AND ELECTRONIC CHARGE 719.50000 719.50115
>>> :NEC02: NUCLEAR AND ELECTRONIC CHARGE 719.50000 719.50000
>>> :NEC03: NUCLEAR AND ELECTRONIC CHARGE 719.50000 719.50000
>>> <case.scfc>
>>> :2P 001: 2P -5.274530454 Ry
>>>
>>> ------- primitive cell, half core-hole
>>> :LABEL4: using the command: run_lapw -ec 0.00001 -p -NI
>>> :WARN : CHARGED CELL with -0.500
>>> :FER : F E R M I - ENERGY(TETRAH.M.)= 0.0944258517
>>> :NEC01: NUCLEAR AND ELECTRONIC CHARGE 179.50000 179.50067
>>> :NEC02: NUCLEAR AND ELECTRONIC CHARGE 179.50000 179.50000
>>> :NEC03: NUCLEAR AND ELECTRONIC CHARGE 179.50000 179.50000
>>> <case.scfc>
>>> :2P 001: 2P -5.268297265 Ry
>>>
>>> --------------
>>>
>>> The energy of the state differs by 6 mRy (85 meV) between the
>>> supercell and the primitive cell, making me hopeful that the
>>> supercell is reasonably converged as to size. The Fermi energy,
>>> though differs by 40 mRy (540 meV), so probably the supercell is not
>>> converged with respect to size for the Fermi energy. In the limit of
>>> a large supercell, it would seem that the Fermi energy should
>>> converge to the Fermi energy for the configuration without the core
>>> hole. So it seems to me that I should use the Fermi energy from the
>>> configuration without the core-hole and compute the binding energy as
>>> -5.2745 - 0.0547 =
>> -5.329 Ry. Is this correct?
>>>
>>> Thanks,
>>> David
>>>
>>> David Olmsted
>>> Assistant Research Engineer
>>> Materials Science and Engineering
>>> 210 Hearst Memorial Mining Building
>>> University of California
>>> Berkeley, CA 94720-1760
>>>
>>>
>>> _______________________________________________
>>> Wien mailing list
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>>> l
>>>
>>
>> --
>> -----------------------------------------
>> Peter Blaha
>> Inst. Materials Chemistry, TU Vienna
>> Getreidemarkt 9, A-1060 Vienna, Austria
>> Tel: +43-1-5880115671
>> Fax: +43-1-5880115698
>> email: pblaha at theochem.tuwien.ac.at
>> -----------------------------------------
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>
>
>
> --
> Professor Laurence Marks
> Department of Materials Science and Engineering Northwestern University
> www.numis.northwestern.edu Corrosion in 4D: MURI4D.numis.northwestern.edu
> Co-Editor, Acta Cryst A "Research is to see what everybody else has seen,
> and to think what nobody else has thought"
> Albert Szent-Gyorgi
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--
Professor Laurence Marks
Department of Materials Science and Engineering
Northwestern University
www.numis.northwestern.edu
Corrosion in 4D: MURI4D.numis.northwestern.edu
Co-Editor, Acta Cryst A
"Research is to see what everybody else has seen, and to think what
nobody else has thought"
Albert Szent-Gyorgi
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