[Wien] Counting the numer of electrons / slightly metallic tail crossing EF
When plotting the DOS of the VB electrons, a large contribution at the interstitial region is simply missing. --H. Wu On Thursday 17 February 2011 15:17, Son Won-joon wrote: Dear WIEN2k Gurus. I am a novice with WIEN2k calculations, and now doing some spin polarized GGA(+U) caculations of Gd-Halide systems. And I have some trivial (but annoying to me) questions: 1. When I check TOTAL CORE-CHARGE of Gd after lstart (and scf file), ?TOTAL CORE-CHARGE: ? ? ? ? ? ? ? ? ? 46.00 ?TOTAL CORE-CHARGE INSIDE SPHERE: ? ? 45.29 ?TOTAL CORE-CHARGE OUTSIDE SPHERE: ? ? 0.71 MAGNETIC MOMENT IN SPHERE seems quite reasonable, but I would like to make sure whether this order of charge leakage can be negligible in total energy calculations (with different spin configurations). I am using the default RMT and R0 values in my struct file. Gd ? ? ? ?NPT= ?781 ?R0=.1 RMT= ? 2.5 ? Z: ?64.0 2. Also, in the end of outputst, OCCUPANCY and ENERGY(RYD) of Gd looks like ... ?4D* ? ? 2.000 ? ?-1.1219532E+01 ?4D* ? ? 2.000 ? ?-1.0774702E+01 ?4D ? ? ?3.000 ? ?-1.0797164E+01 ?4D ? ? ?3.000 ? ?-1.0354003E+01 ?5S ? ? ?1.000 ? ?-3.7282009E+00 ?5S ? ? ?1.000 ? ?-3.4775735E+00 ?5P* ? ? 1.000 ? ?-2.2946120E+00 ?5P* ? ? 1.000 ? ?-2.0836248E+00 ?5P ? ? ?2.000 ? ?-1.9680388E+00 ?5P ? ? ?2.000 ? ?-1.7786762E+00 ?4F* ? ? 3.000 ? ?-7.9075700E-01 ?4F* ? ? 0.000 ? ?-3.9080067E-01 ?4F ? ? ?4.000 ? ?-7.3468784E-01 ?4F ? ? ?0.000 ? ?-3.3752094E-01 ... Since I assigned the default -6.0 Ry for separating core and valence states, 5S and 5P come into my band states. so, I have 5S, 5P and 4F, 5D, 6S in my valence states. When I check NUMBER OF ELECTRONS(:NOE) in scf file as well as the TOTAL CORE-CHARGE of Gd, I can confirm that each Gd has total 18 e-'s in its band states, and QTL values also suggest Gd has 5s and 5p states occupied. And, estimation of the number of electrons from the sum of QTL values is ~ 85 % of :NOE, which I think reasonable. But when I run x tetra to draw the DOS plot, and check outputtdn/up files, the up+dn sum of the NUMBER OF ELECTRONS UP TO EF is about 61 % of the number from :NOE. Even though I exclude the 5S and 5P electrons (10 e-) from counting in :NOE, the number from NUMBER OF ELECTRONS UP TO EF is still smaller. Is it normal to have much smaller (like 2/3) values in outputtdn/up than that of :NOE? Or those two numbers are of different meaning? 3. When I plot the DOS, with settings in int file as ?-0.500 ? 0.1 ? 0.8 ?0.0005 ? ? #Emin, DE, Emax, Gauss-Broad this results in slight VBM tail crossing the EF. I expect from the simple electron countings, this system should shows the gap between VBM and CBM, suspecting this is solely due to the Gaussian broadening. (Even though I use the GGA+U scheme, this tail is still there.) So, I checked outputtup/dn file, and I find I have non-integer occupation number in up spin, like 195.9998, at EF and it sustains the decimal value upto the conduction band minimum. The down spin shows exact interger number of electrons up to EF. I would like to know whether the 0.0002 e- deficiency is due to the numerical error (thus can be neglected), or I should check with the band structure to determine the metallicity of the system. When the number from the outputtup/dn file suggests sort of band gap, then could I consider this system as a semi-conductor regardless of the metallic states tail in dos1up/dn files? And, if 0.0002 e- is due to the numerics, is there any way to remove this annoying number? (I am using RKMAX=8, GMAX=14, and quite large number of kpoints.) I am terribly sorry for bothering you, but I still hope you will give me a kind consideration. Many thanks in advance. Sincerely, Won-joon Son ___ Wien mailing list Wien at zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
[Wien] spin and orbital moment of vanadium
Dear Zhijian, Your current solution may not be wrong but a metastable solution. Since the SOC splitting is about 20 meV for vanadates, LDA+SOC+U calculations with U of several eVs can easily run into different metastable SOC-splitting states. My suggestion is (1) calculate the crystal field level splitting and then think about the likely SOC ground state. (2) play with the density matrix to set the likely ground state and excited states. (3) compare the LDA+U+SOC total energy for the stable solutions in (2). In this respect, my recent publication Spin and orbital states in La1.5Sr0.5CoO4 studied by electronic structure calculations http://link.aps.org/doi/10.1103/PhysRevB.80.081105 may be of your interest. best wishes -- H. Wu On Wednesday 04 November 2009 01:33, Zhijian WU wrote: Dear Novak, Wu hua,and wein3k users, Thanks a lot for your information. Concerning the valence state of V, we just tentatively assigned it as 2+, after careful checking, we found that it closes to 3+ (d^2). The procedure of our calculations is done as Pavel suggested. We first run GGA, then GGA+SOC. After that we run GGA+SOC+U. From GGA+SOC calculation, the orbital moment of V is very small, close to zero (about 0.0x). But even this small orbital moment still paralles with spin moment.After GGA+SOC+U calculation, initially, the orbital moment increases slightly with the increase of U, then after a certain U value, it has a sudden dramatic increase (the dramatic sudden increase has an explanation in a recent paper on MnV2O4 (102, 216405,2009, Phy. Rev. Lett.). During this process, the spin and orbital moments remain parallel. This is indeed weired because we have made many calculations on d orbitals of transition metals (including 3d, 4d and 5d transition metals) and such a strange thing never happened before. Any more suggestions? Thank you very much!! Regards, Zhijian === 2009-11-03 07:37:00 you wrote?=== Dear Zhijian WU, I recommend first to run the calculation without U (then L and S should be antiparallel) and only after it converged switch on the correlation. The reason is that LDA+U stabilizes the occupied states. If you switch it on from the beginning there is a danger that incorrect states will be stabilized. Regards Pavel On Tue, 3 Nov 2009, Zhijian WU wrote: Dear Wien2k users, Recently, we calculated (spin-polarised calculations plus spin-orbit coupling and electron correlation U on vanadium) the spin and orbital moments of vanadium in a transition metal oxides. The valence state of vanadium can be assigned as +2, thus leaving the electronic configuration d^3 for vanadium. From our calculations, it is suprisingly found that the orbital moment paralells with spin moment, which violates the Hund's rule (which states that they should be antiparallel for less than half filled d orbitals). We doubt that something is wrong during our calculations, but can not figure out where or why. Any hint or clue? Thanks a lot for your inputs. Regards, Zhijian ___ Wien mailing list Wien at zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien -- ___ Wien mailing list Wien at zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien = = = = = = = = = = = = = = = = = = = = ___ Wien mailing list Wien at zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
[Wien] Crystal field splitting in empty 3d band of Fe2O3
Dear Y. Ding, For the material Fe2O3 having the formal high-spin Fe3+ and a closed up-spin shell, I think LDA (when giving an insulating solution) or LDA+U partial d-DOS can well show the t2g-eg (if being eigenorbitals) crystal field splitting. Just a note: have you worked with a hexagonal lattice coordinate or a local octahedral coordinate ? May the short Fe-Fe pair or a trigonal field distort too much the crystal field level diagram ? best regards -- H. Wu On Thursday 17 September 2009 07:51, Pavel Novak wrote: Dear Yang Ding, yesterday I forgot third point, which perhaps could give answer to your question. If U is chosen such that it put d-states close to the oxygen p- states, hybridization increases and it shifts the d-levels down if EdEp, or up if EdEp. Regards Pavel On Wed, 16 Sep 2009, Pavel Novak wrote: Dear Yang Ding, care is needed when estimating the crystal field splitting from the LDA+U calculation using the DOS. There are two reasons for it. First, the LDA+U lower the energy of more occupied states and increase the energy of less occupied states. Even if the bands are above Fermi energy, they contain nonzero fraction of electrons (cf :QTL in scf file), which is different for eg and t2g states, hence LDA+U distorts the splitting. Second, the selfinteraction of the d-electrons is present, again distorting the crystal field splitting. Regards Pavel Novak On Tue, 15 Sep 2009, Yang Ding wrote: Dear WIEN2k users, I am really new to WIEN2k, and wondering if you could give your advice and experience on following question concerning the crystal filed splitting calculated from WIEN2k. In order to understand if the pre-edge splitting appearing in the Fe K-edge spectra (1s-4p transition) measured by emission-XANES on Fe2O3 [Groot et al. J. Phys.: Condens. Matter 21 (2009) 104207 http://www.iop.org/EJ/abstract/0953-8984/21/10/104207/], is linked to crystal-filed splitting in 3d empty band. We did a very preliminary ground state calculation using WIEN2k based on GGA+U (and LSDA+U) with U = 4 eV structure to check the crystal field splitting in empty d band above Fermi level. As a result, we found that above 2-6 eV above Fermi level, the energy of t2g is higher than that of eg. This result is similar to what reported by Rollsman et al (PHYSICAL REVIEW B 69, 165107 (2004) http://prola.aps.org/abstract/PRB/v69/i16/e165107) on Fe2O3. In his calculation (GGA/LSDA+U , U= 4eV), the energy of t2g is also higher than that of eg. So my question is why the t2g and eg are reversed in DFT, but the Multiplet calculation gives contradictory results (i.e from Groot et al.). I noticed that Glatzel et al (PHYSICAL REVIEW B 77, 115133 (2008) http://prola.aps.org/abstract/PRB/v69/i16/e165107) reported that they obtained the right crystal field splitting using (LDA+U, U=6 eV) from WIEN2k. So we wonder if we might missed something in the calculations? Thanks in advance for your help,
[Wien] electron transfer - RMT spheres
You may have to set an equal muffin-tin size, to say ~2 a.u. for the same element Co at inequivalent sites. When talking about charge transfer or charge ordering, it is better to look at the orbital occupation number rather than the total charge (within MT sphere), since the former can tell you the formal valence state. Normally, covalency reduces the nominal charge difference and thus leads to a smaller difference of the 1s core levels of the Co1 and Co2 than expected from a pure ionic model. But I guess the core level energy difference should be still observable in the calculations. regards -- H. Wu On Thursday 27 August 2009 18:26, Gheorghe P wrote: Dear Wien users, I am studying a system which has a structural transition; above the structural transition all the Co ions are in equivalent positions having an octahedral environment with oxygen ions in the corners of the octahedra (distance Co-O = 1.95); below the structural transition the oxygen ions move such that there will be two inequivalent sites for Co after the distortion; Co1 will be inside a contracted octahedra (Co-O = 1.91) and Co2 will be inside an expanded octahedra (Co-O = 2.02). From some measurements I expect that at the structural transition there is a electron transfer from the Co1 site to the Co2 site; to test this scenario I did an experiment using resonant X-ray scattering at the Co K edge; during the scattering an electron from the 1s level is moved into an empty 4p state (for a very short time); so in my case I will have (for both Co1 and Co2) a shift of the 1s level due to the electron transfer and in the same time I will have a shift of the 4p states due to the hybridization of the Co 4p states with O 2p states. I would like to calculate these shifts of the 1s and 4p level for both Co1 and Co2 and to obtain a quantitatively value for the electron transfer using WIEN2k but i have a question about how to set up the RMT spheres around the Co ions during the calculations. I read so far in the emailing list (see below) that if I want to obtain a approximate value for the electron transfer I have to look at the charge in the RMT spheres. My question is about how to set the RMT sphere for the two ions Co1 and Co2? I did a non-magnetic calculation using the w2web interface; if I use the default program from the w2web graphical interface, the calculated spheres for Co1 and Co2 are identical and there is no electron transfer between the two spheres; but in the reality if there is an electron transfer the ionic radius of Co1 and Co2 would be different. So how do I have to set up the sphere such that the calculations model as good as possible my system??? Thank you very much in advance for any help you can give me to understand how to model this problem. Best wishes, Lucian ++ Jorissen Kevin Kevin.Jorissen at ua.ac.be Tue Nov 4 13:43:42 CET 2003 Previous message: [Wien] Large no of K-points in the IBZ Next message: [Wien] Error in nn of a supercell Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] Some possibilities : * draw charge density maps and difference density maps * do Bader analysis * look at the charges in the MT Eg. in PRB67 075102 you'll find these three methods ?used and compared (APW calculations of Cu2O). As there is no unambiguous definition of charge transfer, different methods will yield different quantitative values. But you can hope to discover trends. Kevin.
