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 <olms...@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-boun...@zeus.theochem.tuwien.ac.at > [mailto:wien-boun...@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 >> Wien@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 >> > > -- > ----------------------------------------- > Peter Blaha > Inst. Materials Chemistry, TU Vienna > Getreidemarkt 9, A-1060 Vienna, Austria > Tel: +43-1-5880115671 > Fax: +43-1-5880115698 > email: pbl...@theochem.tuwien.ac.at > ----------------------------------------- > _______________________________________________ > Wien mailing list > Wien@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 > > _______________________________________________ > Wien mailing list > Wien@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 -- 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 _______________________________________________ Wien mailing list Wien@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