Dear Matteo, It seems i have found the problem. It's not the problem of the xcoordcrys. I set it as .true. and the polarization vectors are (0,0,1) and (0,1,0). The xray k vector is the default value (1,0,0). BTW, can we use the same vector for polarization and xay k moment? e.g. Both of them are (1,0,0). Is it OK?
The problem i found is that i set the "cut_occ_states" = .true. Then it cut all the occupied state that i expected to see. When i reset it to .false., i saw the expected peak. I have another problem, what does the "ef_r" do in the calculation? For instance, i got fermi level of -5 eV with scf calculation. The i set ef_r= -5/13.6 Ry. Then, in the calculated xspectra data, where is the Fermi level? It is ajusted to 0 eV, or still is the -5 eV? Sorry to bother you again. Thanks so much. Cheers, Min Wu 2010-10-18 >From: Matteo Calandra <matteo.calandra at impmc.jussieu.fr> >Reply-To: PWSCF Forum <pw_forum at pwscf.org> >To: pw_forum at pwscf.org >Subject: Re:[Pw_forum] xspectra calculation (wumindt2) >Date: Mon, 18 Oct 2010 09:35:10 +0200 > >dear Min Wu, > > the attachment do not go through the pw_forum, so I cannot >do much about it. What I can tell you is that we calculate >Co and LiCoO2 and we get a good agreement with experiments. >Maybe you can try to compare with the following paper: > >Juhin et al. Phys. Rev. B 81, 115115 (2010) >http://link.aps.org/doi/10.1103/PhysRevB.81.115115 > >Anyway, from four message what seems to be wrong (assuming the scf >run to be correct) are the unit of the polarization vector >(assuming you're dealing with the dipolar part only and assuming >the peak you're referring to is dipolar). Did you set xcoordcrys to >the proper value (see below)? > >For zhqt concerns CoO2, note that the pre-edge >of CoO2 at the Co K-edge has a quadrupolar part, so if you stick >to the dipolar calculation you want be able to reproduce the pre-edge >peak. Note also that in the case of LiCoO2, which is probably >not so different from yours, DFT fails in the >pre-edge and you have to use DFT+U. > >In particular, remember that if you don't set the variable >xcoordcrys=.false. your xepsilon and xkvec are in reduced coordinates. > From Doc/INPUT_XSPECTRA > >xkvec(1:3) real(DP) >DEFAULT=(1.0,0 >.0,0.0) > coordinates of the x-ray momentum k > > >xepsilon(1:3) real(DP) >DEFAULT=(1.0,0 >.0,0.0) > coordinates of the incident x-ray > polarization vector > >xcoordcrys logical >DEFAULT=.true. > .true. to use crystal coordinates for > k and epsilon > > >Maybe you could try to reproduce our calculation on LiCoO2 so that >you are sure of not having any errors with the input file. >The paper is very detailed so you can compare every step in the calculation. > >All the best, M. > > >Message: 6 > >Date: Mon, 18 Oct 2010 05:03:50 +0800 > >From: "wumindt2" > >Subject: Re: [Pw_forum] Xspectra calculation (wumindt2) > >To: pw_forum at pwscf.org > >Message-ID: > >Content-Type: text/plain; charset="gb2312" > > >Dear Matteo, > > >I met some problem when calculating the XASs with the Xspectra. > >I tested the example of quartz, and got the consistent result with the > >published work. > >Then i moved on to test another example of solid CO2, which has an > >isotropic > >symmetry according to C. Brouder's paper. But the X-ray absorption > >spectrum > >i got was totally wrong. The first sharp peak which is well-known > >existing > >in CO2 was not found. > >We also tested a single CO2 molecule which is still a clear-cut >example. > >The C atom and the two O atoms are all in the Z axis. So the > >polarization vectors > >of (0,0,1) and (1,0,0) are enough for this case. However, we still > >cannot get the > >right XAS. To make it easier for you to understand my problem, I > >attached the input files of this calculation. > >The GIPAW pseudopotentials i used were downloaded from the website of >QE. > > >Thanks a lot for the help. > > >Best regards, > > >Min Wu >_______________________________________________ >Pw_forum mailing list >Pw_forum at pwscf.org >http://www.democritos.it/mailman/listinfo/pw_forum >
