[Wien] Fwd: not getting convergence with MBJ potential
Dear wien2k users, Any response of my previous mail will be very helpful for us. Eagerly waiting for your comments. with regards, -- Forwarded message -- From: shamik chakrabarti shamik...@gmail.com Date: Sun, Dec 11, 2011 at 5:42 PM Subject: not getting convergence with MBJ potential To: A Mailing list for WIEN2k users wien at zeus.theochem.tuwien.ac.at Dear wien2k users, I am trying to simulate electronic structure of a charge transfer insulator. Our system consists of a unit cell having 56 atoms and we are using 14 k-points. As GGA+U method was failed to reproduce the proper band gap (in fact much less than the experimentally obtained one) we have opted for MBJ potential. *Initially the mixing parameter was set to 0.2 and we got Ghost band error after few iterations. Hence we reduce the mixing parameter to 0.15.* Until now still it has shown no error except some extra message in case.dayfile. I am giving those messages below. So far e.c. c.c were achieved up to 2.239... 5.4599 respectively and already 36 iterations are over. My questions are: (1) Is it ok to set up a mixing parameter of 0.15 that is with it, is it possible to reach convergence? (2) As plain GGA takes around 80 iterations to converge, is it that MBJ potential will take much higher than that as we know it is always hard to get convergence with this method? (3) what are the meanings of the given messages below: lapw2 -c -up -vresp (17:12:13)lapw1 -c -dn (16:19:33) 10848.369u 98.026s 52:39.78 346.4% 0+0k 0+1099920io 0pf+0w lapw1 -c -up (15:26:49) 10864.462u 99.082s 52:44.39 346.4% 0+0k 0+1100232io 0pf+0w 460.324u 151.313s 6:52.62 148.2% 0+0k 0+732368io 0pf+0w -5.956509016536202E-002 3.325214690385789E-002 -9.166205529297161E-002 tauwrong= int:rho,tauw,grho,g2rho 2.146196813781874E-002 1.287982148952303E-002 -4.564940741427861E-002 3.061850458947012E-002 -5.357427363703868E-002 tauwrong= int:rho,tauw,grho,g2rho 1.778719641126464E-002 1.317651193616000E-002 *what is tauwrong?* -4.561631481999567E-002 3.051935798833875E-002 -5.372842413400847E-002 tauwrong= int:rho,tauw,grho,g2rho 1.783702549056333E-002 1.305474408433668E-002 -2.872847342414767E-002 2.625149916992486E-002 -2.271097056901070E-002 tauwrong= int:rho,tauw,grho,g2rho 1.456340274765583E-002 1.183001700580401E-002 -2.843529510619935E-002 2.60760246414E-002 -2.279192386903682E-002 tauwrong= int:rho,tauw,grho,g2rho 1.462794826548238E-002 1.162089194449066E-002 -1.211083415464120E-002 .. .. lapw0 (15:19:56) sphere:rho,tauw,grho,g2rho 7.4687572237 180.956718336004 lapw0 -grr (15:15:10) 315.375u 93.253s 4:45.73 143.0% 0+0k 0+ Any response in this regard will be very helpful for us. Thanks in advance. with regards, -- Shamik Chakrabarti Senior Research Fellow Dept. of Physics Meteorology Material Processing Solid State Ionics Lab IIT Kharagpur Kharagpur 721302 INDIA -- Shamik Chakrabarti Senior Research Fellow Dept. of Physics Meteorology Material Processing Solid State Ionics Lab IIT Kharagpur Kharagpur 721302 INDIA -- next part -- An HTML attachment was scrubbed... URL: http://zeus.theochem.tuwien.ac.at/pipermail/wien/attachments/20111212/4b59b578/attachment.htm
[Wien] Fwd: not getting convergence with MBJ potential
Hello, It is strange that you have such a bad convergence on the energy and the charge after that many cycles. My feeling is that something is wrong in the input. Have a look at the user manual. From page 205 on, there is an explanation of the meaning of ghost bands. You have to experiment on your chemical system to get rid of them. Pascal On 12/12/2011 05:21, shamik chakrabarti wrote: Dear wien2k users, Any response of my previous mail will be very helpful for us. Eagerly waiting for your comments. with regards, -- Forwarded message -- From: *shamik chakrabarti* shamikphy at gmail.com mailto:shamikphy at gmail.com Date: Sun, Dec 11, 2011 at 5:42 PM Subject: not getting convergence with MBJ potential To: A Mailing list for WIEN2k users wien at zeus.theochem.tuwien.ac.at mailto:wien at zeus.theochem.tuwien.ac.at Dear wien2k users, I am trying to simulate electronic structure of a charge transfer insulator. Our system consists of a unit cell having 56 atoms and we are using 14 k-points. As GGA+U method was failed to reproduce the proper band gap (in fact much less than the experimentally obtained one) we have opted for MBJ potential. *Initially the mixing parameter was set to 0.2 and we got Ghost band error after few iterations. Hence we reduce the mixing parameter to 0.15.* Until now still it has shown no error except some extra message in case.dayfile. I am giving those messages below. So far e.c. c.c were achieved up to 2.239... 5.4599 respectively and already 36 iterations are over. My questions are: (1) Is it ok to set up a mixing parameter of 0.15 that is with it, is it possible to reach convergence? (2) As plain GGA takes around 80 iterations to converge, is it that MBJ potential will take much higher than that as we know it is always hard to get convergence with this method? (3) what are the meanings of the given messages below: lapw2 -c -up -vresp (17:12:13)lapw1 -c -dn(16:19:33) 10848.369u 98.026s 52:39.78 346.4%0+0k 0+1099920io 0pf+0w lapw1 -c -up(15:26:49) 10864.462u 99.082s 52:44.39 346.4%0+0k 0+1100232io 0pf+0w 460.324u 151.313s 6:52.62 148.2%0+0k 0+732368io 0pf+0w -5.956509016536202E-002 3.325214690385789E-002 -9.166205529297161E-002 tauwrong= int:rho,tauw,grho,g2rho 2.146196813781874E-002 1.287982148952303E-002 -4.564940741427861E-002 3.061850458947012E-002 -5.357427363703868E-002 tauwrong= int:rho,tauw,grho,g2rho 1.778719641126464E-002 1.317651193616000E-002*what is tauwrong?* -4.561631481999567E-002 3.051935798833875E-002 -5.372842413400847E-002 tauwrong= int:rho,tauw,grho,g2rho 1.783702549056333E-002 1.305474408433668E-002 -2.872847342414767E-002 2.625149916992486E-002 -2.271097056901070E-002 tauwrong= int:rho,tauw,grho,g2rho 1.456340274765583E-002 1.183001700580401E-002 -2.843529510619935E-002 2.60760246414E-002 -2.279192386903682E-002 tauwrong= int:rho,tauw,grho,g2rho 1.462794826548238E-002 1.162089194449066E-002 -1.211083415464120E-002 .. .. lapw0 (15:19:56) sphere:rho,tauw,grho,g2rho 7.4687572237 180.956718336004 lapw0 -grr (15:15:10) 315.375u 93.253s 4:45.73 143.0%0+0k 0+ Any response in this regard will be very helpful for us. Thanks in advance. with regards, -- Shamik Chakrabarti Senior Research Fellow Dept. of Physics Meteorology Material Processing Solid State Ionics Lab IIT Kharagpur Kharagpur 721302 INDIA -- Shamik Chakrabarti Senior Research Fellow Dept. of Physics Meteorology Material Processing Solid State Ionics Lab IIT Kharagpur Kharagpur 721302 INDIA ___ Wien mailing list Wien at zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien -- Dr. pascal Boulet, computational chemist University of Aix-Marseille I Laboratoire Chimie Provence, UMR 6264 Group of Theoretical Chemistry Avenue Normandie-Niemen 13397 Marseille Cedex 20 France ** Tel. (+33) (0)413.55.18.10 Fax. (+33) (0)413.55.18.50 ** http://www.lc-provence.fr https://sites.google.com/a/univ-provence.fr/pb-comput-chem %% * Fran?ais - d?tect? * Anglais * Fran?ais * Anglais * Fran?ais javascript:void(0);
[Wien] Fwd: not getting convergence with MBJ potential
When you need 80 iterations with GGA, it is rather clear that also mBJ will take a long time (usually a bit longer ). Anyway: Have you checked the forces (total, not partial !!) in the GGA calculation. Small forces will tell you that your structure is probably ok, large forces (gt. 10-20) means that the structure is NOT ok. The TAUWRONG messages indicate, that the kinetic energy density is not accurate (we check some known constrains like positive tau, comparison with tau-weiz?cker,, and limit wrong values. Something like this may happen at the beginning of mBJ, but usually indicate that the calculations are not well converged (RKmax, GMAX ?) or the vresp file and the clmsum file do not match properly. PRATT with 0.15 at the beginning should be fine. Usually, after 10-20 iterations one should see grep :DIS case.scf starting to decrease slightly but steadily. At this stage one can usually switch to MSR1 to accelerate convergence. BUT: If this is a transition metal compound and the gap is expected between partially occupied d-bands, but LDA+U does not give a gap, then I also expect that something is wrong with the (magnetic ??) structure ... E.g.: a ferromagnetic solution will stay magnetic, while a PROPER AFM structure may give an insulator. Am 12.12.2011 08:45, schrieb shamik chakrabarti: Dear Dr. Pascal, As we were getting Ghost band error due to large charge fluctuation during initial cycle *we have reduced the mixing parameter from 0.2 to 0.15 hence thereafter we have not received ghost band error yet.* As long as variation of RMT is concerned the variation is only from 1.7 to 2.01 in the structure. So far there is no energy equivalence between a local orbital and overall energy parameter which can induce ghost band error. Also we have achieved convergence of -0.34 with plain GGA and only with MBJ potential we are getting the convergence problem and again plain GGA and also GGA+U have not given the proper electronic structure. As far as the structure is concerned we are very much sure about its structural parameters as they are giving the same XRD as experiment when the positional coordinates and lattice parameters of the 56 atom cell were put into a software powdcell. looking forwards to your comments. with regards, On Mon, Dec 12, 2011 at 12:26 PM, pascal boulet pascal.boulet at univ-provence.fr mailto:pascal.boulet at univ-provence.fr wrote: Hello, It is strange that you have such a bad convergence on the energy and the charge after that many cycles. My feeling is that something is wrong in the input. Have a look at the user manual. From page 205 on, there is an explanation of the meaning of ghost bands. You have to experiment on your chemical system to get rid of them. Pascal On 12/12/2011 05:21, shamik chakrabarti wrote: Dear wien2k users, Any response of my previous mail will be very helpful for us. Eagerly waiting for your comments. with regards, -- Forwarded message -- From: *shamik chakrabarti* shamikphy at gmail.com mailto:shamikphy at gmail.com mailto:shamikphy at gmail.com mailto:shamikphy at gmail.com Date: Sun, Dec 11, 2011 at 5:42 PM Subject: not getting convergence with MBJ potential To: A Mailing list for WIEN2k users wien at zeus.theochem.tuwien.ac.at mailto:wien at zeus.theochem.tuwien.ac.at mailto:wien at zeus.theochem.tuwien.ac.at mailto:wien at zeus.theochem.tuwien.ac.at Dear wien2k users, I am trying to simulate electronic structure of a charge transfer insulator. Our system consists of a unit cell having 56 atoms and we are using 14 k-points. As GGA+U method was failed to reproduce the proper band gap (in fact much less than the experimentally obtained one) we have opted for MBJ potential. *Initially the mixing parameter was set to 0.2 and we got Ghost band error after few iterations. Hence we reduce the mixing parameter to 0.15.* Until now still it has shown no error except some extra message in case.dayfile. I am giving those messages below. So far e.c. c.c were achieved up to 2.239... 5.4599 respectively and already 36 iterations are over. My questions are: (1) Is it ok to set up a mixing parameter of 0.15 that is with it, is it possible to reach convergence? (2) As plain GGA takes around 80 iterations to converge, is it that MBJ potential will take much higher than that as we know it is always hard to get convergence with this method? (3) what are the meanings of the given messages below: lapw2 -c -up -vresp (17:12:13)lapw1 -c -dn(16:19:33) 10848.369u 98.026s 52:39.78
[Wien] Fwd: not getting convergence with MBJ potential
Dear Dr. Chakrabarti, All right. So, another idea: could it be that you restarted your m-BJ calculation using the converged GGA or GGA+U density? I ran into these kinds of troubles several times. I found it preferable to start from scratch... Hope this help, Pascal On 12/12/2011 08:45, shamik chakrabarti wrote: Dear Dr. Pascal, As we were getting Ghost band error due to large charge fluctuation during initial cycle *we have reduced the mixing parameter from 0.2 to 0.15 hence thereafter we have not received ghost band error yet.* As long as variation of RMT is concerned the variation is only from 1.7 to 2.01 in the structure. So far there is no energy equivalence between a local orbital and overall energy parameter which can induce ghost band error. Also we have achieved convergence of -0.34 with plain GGA and only with MBJ potential we are getting the convergence problem and again plain GGA and also GGA+U have not given the proper electronic structure. As far as the structure is concerned we are very much sure about its structural parameters as they are giving the same XRD as experiment when the positional coordinates and lattice parameters of the 56 atom cell were put into a software powdcell. looking forwards to your comments. with regards, On Mon, Dec 12, 2011 at 12:26 PM, pascal boulet pascal.boulet at univ-provence.fr mailto:pascal.boulet at univ-provence.fr wrote: Hello, It is strange that you have such a bad convergence on the energy and the charge after that many cycles. My feeling is that something is wrong in the input. Have a look at the user manual. From page 205 on, there is an explanation of the meaning of ghost bands. You have to experiment on your chemical system to get rid of them. Pascal On 12/12/2011 05:21, shamik chakrabarti wrote: Dear wien2k users, Any response of my previous mail will be very helpful for us. Eagerly waiting for your comments. with regards, -- Forwarded message -- From: *shamik chakrabarti* shamikphy at gmail.com mailto:shamikphy at gmail.com mailto:shamikphy at gmail.com mailto:shamikphy at gmail.com Date: Sun, Dec 11, 2011 at 5:42 PM Subject: not getting convergence with MBJ potential To: A Mailing list for WIEN2k users wien at zeus.theochem.tuwien.ac.at mailto:wien at zeus.theochem.tuwien.ac.at mailto:wien at zeus.theochem.tuwien.ac.at mailto:wien at zeus.theochem.tuwien.ac.at Dear wien2k users, I am trying to simulate electronic structure of a charge transfer insulator. Our system consists of a unit cell having 56 atoms and we are using 14 k-points. As GGA+U method was failed to reproduce the proper band gap (in fact much less than the experimentally obtained one) we have opted for MBJ potential. *Initially the mixing parameter was set to 0.2 and we got Ghost band error after few iterations. Hence we reduce the mixing parameter to 0.15.* Until now still it has shown no error except some extra message in case.dayfile. I am giving those messages below. So far e.c. c.c were achieved up to 2.239... 5.4599 respectively and already 36 iterations are over. My questions are: (1) Is it ok to set up a mixing parameter of 0.15 that is with it, is it possible to reach convergence? (2) As plain GGA takes around 80 iterations to converge, is it that MBJ potential will take much higher than that as we know it is always hard to get convergence with this method? (3) what are the meanings of the given messages below: lapw2 -c -up -vresp (17:12:13)lapw1 -c -dn(16:19:33) 10848.369u 98.026s 52:39.78 346.4%0+0k 0+1099920io 0pf+0w lapw1 -c -up(15:26:49) 10864.462u 99.082s 52:44.39 346.4%0+0k 0+1100232io 0pf+0w 460.324u 151.313s 6:52.62 148.2%0+0k 0+732368io 0pf+0w -5.956509016536202E-002 3.325214690385789E-002 -9.166205529297161E-002 tauwrong= int:rho,tauw,grho,g2rho 2.146196813781874E-002 1.287982148952303E-002 -4.564940741427861E-002 3.061850458947012E-002 -5.357427363703868E-002 tauwrong= int:rho,tauw,grho,g2rho 1.778719641126464E-002 1.317651193616000E-002*what is tauwrong?* -4.561631481999567E-002 3.051935798833875E-002 -5.372842413400847E-002 tauwrong= int:rho,tauw,grho,g2rho 1.783702549056333E-002 1.305474408433668E-002 -2.872847342414767E-002 2.625149916992486E-002 -2.271097056901070E-002 tauwrong= int:rho,tauw,grho,g2rho 1.456340274765583E-002 1.183001700580401E-002 -2.843529510619935E-002 2.60760246414E-002 -2.279192386903682E-002
[Wien] Fwd: not getting convergence with MBJ potential
I wonder whether you really have the structure right. a) When you say that you get the same structure, what R-factor? Powder diffraction is not very sensitive to oxygen positions in the presence of heavy metal atoms. b) If GGA takes about 80 iterations I suspect that you have a metal. If you do not have the correct number of oxygen versus metal atoms you will get this, and no amount of U or mBJ will change this (in 99% of cases). Check the bond-valence sums of your model, are the numbers reasonable? This is a standard test in solid-state chemistry. c) Do you have large forces (as Peter asked)? If you do this also indicates that you have the structure wrong. d) When you say that you were using a greed of 0.2 (please do not use the term mixing factor, it is misleading) was this for Pratt or MSR1? A change from 0.2 to 0.15 with MSR1 will not matter much. 2011/12/12 shamik chakrabarti shamikphy at gmail.com: Dear Dr Peter Blaha and Dr Pascal, ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? The material is a ferrimagnetic transition metal compound and a charge transfer insulator and the gap is between d and O p states. Yes we have started MBJ potential calculation from the converged GGA charge density. So what we can do, we can start from the scratch with MBJ potential and after few iterations will get shifted to MSR1 mixing to improve the convergence. We hope that will help. Thank you for all your helps. with regards, On Mon, Dec 12, 2011 at 1:31 PM, pascal boulet pascal.boulet at univ-provence.fr wrote: Dear Dr. Chakrabarti, All right. So, another idea: could it be that you restarted your m-BJ calculation using the converged GGA or GGA+U density? I ran into these kinds of troubles several times. I found it preferable to start from scratch... Hope this help, Pascal On 12/12/2011 08:45, shamik chakrabarti wrote: Dear Dr. Pascal, ? ? ? ? ? ? ? ? As we were getting Ghost band error due to large charge fluctuation during initial cycle *we have reduced the mixing parameter from 0.2 to 0.15 hence thereafter we have not received ghost band error yet.* As long as variation of RMT is concerned the variation is only from 1.7 to 2.01 in the structure. So far there is no energy equivalence between a local orbital and overall energy parameter which can induce ghost band error. Also we have achieved convergence of -0.34 with plain GGA and only with MBJ potential we are getting the convergence problem and again plain GGA and also GGA+U have not given the proper electronic structure. As far as the structure is concerned we are very much sure about its structural parameters as they are giving the same XRD as experiment when the positional coordinates and lattice parameters of the 56 atom cell were put into a software powdcell. looking forwards to your comments. with regards, On Mon, Dec 12, 2011 at 12:26 PM, pascal boulet pascal.boulet at univ-provence.fr mailto:pascal.boulet at univ-provence.fr wrote: ? ? Hello, ? ? It is strange that you have such a bad convergence on the energy ? ? and the ? ? charge after that many cycles. ? ? My feeling is that something is wrong in the input. ? ? Have a look at the user manual. From page 205 on, there is an ? ? explanation of the meaning of ghost bands. You have to experiment on ? ? your chemical system to get rid of them. ? ? Pascal ? ? On 12/12/2011 05:21, shamik chakrabarti wrote: ? ? Dear wien2k users, ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?Any response of my previous mail will be very ? ? helpful for us. Eagerly waiting for your comments. ? ? ? ? with regards, ? ? ? ? -- Forwarded message -- ? ? From: *shamik chakrabarti* shamikphy at gmail.com ? ? mailto:shamikphy at gmail.com ? ? mailto:shamikphy at gmail.com mailto:shamikphy at gmail.com ? ? Date: Sun, Dec 11, 2011 at 5:42 PM ? ? Subject: not getting convergence with MBJ potential ? ? To: A Mailing list for WIEN2k users ? ? wien at zeus.theochem.tuwien.ac.at ? ? mailto:wien at zeus.theochem.tuwien.ac.at ? ? mailto:wien at zeus.theochem.tuwien.ac.at ? ? mailto:wien at zeus.theochem.tuwien.ac.at ? ? ? ? ? ? Dear wien2k users, ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?I am trying to simulate electronic ? ? structure of ? ? a charge transfer insulator. Our system consists of a unit cell ? ? having ? ? 56 atoms and we are using 14 k-points. As GGA+U method was failed to ? ? reproduce the proper band gap (in fact much less than the ? ? experimentally obtained one) we have opted for MBJ potential. ? ? *Initially the mixing parameter was set to 0.2 and we got Ghost band ? ? error after few iterations. Hence we reduce the mixing parameter to ? ? 0.15.* Until now still it has shown no error except some extra ? ? message ? ? in case.dayfile. I am giving those messages below. So far e.c. c.c ? ? were achieved up to 2.239...
[Wien] Fwd: not getting convergence with MBJ potential
at zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien -- Dr. pascal Boulet, computational chemist University of Aix-Marseille I Laboratoire Chimie Provence, UMR 6264 Group of Theoretical Chemistry Avenue Normandie-Niemen 13397 Marseille Cedex 20 France ** Tel. (+33) (0)413.55.18.10 Fax. (+33) (0)413.55.18.50 ** http://www.lc-provence.fr https://sites.google.com/a/univ-provence.fr/pb-comput-chem %% * Fran?ais - d?tect? * Anglais * Fran?ais * Anglais * Fran?ais javascript:void(0); ___ Wien mailing list Wien at zeus.theochem.tuwien.ac.at mailto:Wien at zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien -- Shamik Chakrabarti Senior Research Fellow Dept. of Physics Meteorology Material Processing Solid State Ionics Lab IIT Kharagpur Kharagpur 721302 INDIA ___ Wien mailing list Wien at zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien -- Dr. pascal Boulet, computational chemist University of Aix-Marseille I Laboratoire Chimie Provence, UMR 6264 Group of Theoretical Chemistry Avenue Normandie-Niemen 13397 Marseille Cedex 20 France ** Tel. (+33) (0)413.55.18.10 Fax. (+33) (0)413.55.18.50 ** http://www.lc-provence.fr https://sites.google.com/a/univ-provence.fr/pb-comput-chem %% ___ Wien mailing list Wien at zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien -- Shamik Chakrabarti Senior Research Fellow Dept. of Physics Meteorology Material Processing Solid State Ionics Lab IIT Kharagpur Kharagpur 721302 INDIA ___ Wien mailing list Wien at zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien -- Professor Laurence Marks Department of Materials Science and Engineering Northwestern University www.numis.northwestern.edu 1-847-491-3996 Research is to see what everybody else has seen, and to think what nobody else has thought Albert Szent-Gyorgi ___ Wien mailing list Wien at zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien -- Shamik Chakrabarti Senior Research Fellow Dept. of Physics Meteorology Material Processing Solid State Ionics Lab IIT Kharagpur Kharagpur 721302 INDIA -- next part -- An HTML attachment was scrubbed... URL: http://zeus.theochem.tuwien.ac.at/pipermail/wien/attachments/20111212/5f904a86/attachment-0001.htm
[Wien] Fwd: not getting convergence with MBJ potential
If your structure is a metal in GGA in 99% of cases it will be a metal in GGA+U and mBJ. And, it is wrong. Just because others reported the structure does not mean that it is right! There are many cases where someone reported a structure, others followed their lead and only later someone pointed out that it was wrong. Look at your GGA (or GGA+U) result, the overall DOS which is in case.output2up/dn (or do a standard DOS calculation). If the positions are close to correct you should see a gap between the different bands. If you have electrons at E_F at the bottom of a band (metal d) your structure is reduced; you will need some metal vacancies. If there are holes at the top of the oxygen band your structure is oxidized -- you will need some oxygen vacancies. Note that vacancies can be ordered or disordered (partial occupancies) and simulating these is not easy. Check the bond-valence sums, they are probably given by the powder diffraction fitting program or there are many codes to do this. You can even do a grep -e bond case.outputnn to get a decent number. All the O's should be close to 2 (perhaps in the range 1.8-2.2) and all the metals should be in reasonable states. For instance a value of 3.5 for Ti means that it is reduced, and a value of 4.5 means that something is badly wrong. As a shameless plug look at Surface Science doi:10.1016/j.susc.2011.10.018 and references therein, or for instance I.D. Brown, Chem. Rev. 109 (2009). In my opinion BVS is a simple and very quick way to do a sanity check and can save you from weeks of not useful DFT calculations. 2011/12/12 shamik chakrabarti shamikphy at gmail.com: Dear Dr. Laurence Marks Sir, I am giving the answers all of your queries below, a) If R-factor means reliability factor then we have achieved a parameter called goodness of fit whose value was 1.0038. But this material was prepared previously by researchers and they have also got the same structure. Although the structure is based only on the Rietveld fitting of experimental XRD pattern. There was no rigorous TEM analysis on this structure so far. b) We have done UV-visible band gap measurement on this material and it is 3.26 eV. But as you have said properly it is indeed coming as metal after getting converged in 80 iterations. But we have noticed that there are presence of O p orbital between upper and lower Hubbard band of transition metal atom and hence GGA+U will not improve the situation. c) At the moment we are a bit handicapped for doing Geometrical (both lattice parameter and atomic coordinates) optimization of 56 atoms unit cell structure as we do not have the facility of cluster. Hence as a first approximation we are first trying to reach as near as possible to the accurate electronic structure. We are soon going to get the facility and then we can use geometrical optimization. And hence we really do have large forces on the structure. d) We have used a greed of 0.2 and 0.15 both for PRATT mixing and we have not used MSR1 mixing for mbj potential yet. Sir, as far as the above discussion is concerned we might have our structure wrong (need more accurate TEM analysis!) or Geometrical optimization may solve the problem. But as we are now trying to experiment with test run we and as it seems GGA+U can not solve the problem we have opted for mbj potential. But as you have said if the structure is wrong (we are not yet confirmed though) we may never reach the convergence or desired electronic structure! Thank you very much for your help Sir. On Mon, Dec 12, 2011 at 6:52 PM, Laurence Marks L-marks at northwestern.edu wrote: I wonder whether you really have the structure right. a) When you say that you get the same structure, what R-factor? Powder diffraction is not very sensitive to oxygen positions in the presence of heavy metal atoms. b) If GGA takes about 80 iterations I suspect that you have a metal. If you do not have the correct number of oxygen versus metal atoms you will get this, and no amount of U or mBJ will change this (in 99% of cases). Check the bond-valence sums of your model, are the numbers reasonable? This is a standard test in solid-state chemistry. c) Do you have large forces (as Peter asked)? If you do this also indicates that you have the structure wrong. d) When you say that you were using a greed of 0.2 (please do not use the term mixing factor, it is misleading) was this for Pratt or MSR1? A change from 0.2 to 0.15 with MSR1 will not matter much. 2011/12/12 shamik chakrabarti shamikphy at gmail.com: Dear Dr Peter Blaha and Dr Pascal, ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? The material is a ferrimagnetic transition metal compound and a charge transfer insulator and the gap is between d and O p states. Yes we have started MBJ potential calculation from the converged GGA charge density. So what we can do, we can start from the scratch with MBJ potential and after few iterations will get shifted to
[Wien] Fwd: not getting convergence with MBJ potential
If your geometry is not correct, you cannot expect that the bandgaps are correct or even metal/insulator state comes out correctly. The experimental lattice parameters are usually ok, even in the simplest experiments, but the positions of light elements (oxygen) vs. heavier ones are NOT. Thus I would take the exp. lattice parameters, but when forces are big (10-20 mRy/bohr), you need to run a couple of min steps. In all charge-transfer insulators you have the gap between O-2p and TM-d states and you CAN influence the gap by LDA+U. Larger U simply shifts the upper Hubbard band up and makes a larger gap to O-2p. (PS: I'm not arguing that LDA+U necessarily describes the physics correctly, but usually it does what one tells it). PPS: Have you done optics ? Eventually matrix elements may influence the absorption and you cannot just look into the DOS. b) We have done UV-visible band gap measurement on this material and it is 3.26 eV. But as you have said properly it is indeed coming as metal after getting converged in 80 iterations. But we have noticed that there are presence of O p orbital between upper and lower Hubbard band of transition metal atom and hence GGA+U will not improve the situation. c) At the moment we are a bit handicapped for doing Geometrical (both lattice parameter and atomic coordinates) optimization of 56 atoms unit cell structure as we do not have the facility of cluster. Hence as a first approximation we are first trying to reach as near as possible to the accurate electronic structure. We are soon going to get the facility and then we can use geometrical optimization. And hence we really do have large forces on the structure. d) We have used a greed of 0.2 and 0.15 both for PRATT mixing and we have not used MSR1 mixing for mbj potential yet. Sir, as far as the above discussion is concerned we might have our structure wrong (need more accurate TEM analysis!) or Geometrical optimization may solve the problem. But as we are now trying to experiment with test run we and as it seems GGA+U can not solve the problem we have opted for mbj potential. But as you have said if the structure is wrong (we are not yet confirmed though) we may never reach the convergence or desired electronic structure! Thank you very much for your help Sir. On Mon, Dec 12, 2011 at 6:52 PM, Laurence Marks L-marks at northwestern.edu mailto:L-marks at northwestern.edu wrote: I wonder whether you really have the structure right. a) When you say that you get the same structure, what R-factor? Powder diffraction is not very sensitive to oxygen positions in the presence of heavy metal atoms. b) If GGA takes about 80 iterations I suspect that you have a metal. If you do not have the correct number of oxygen versus metal atoms you will get this, and no amount of U or mBJ will change this (in 99% of cases). Check the bond-valence sums of your model, are the numbers reasonable? This is a standard test in solid-state chemistry. c) Do you have large forces (as Peter asked)? If you do this also indicates that you have the structure wrong. d) When you say that you were using a greed of 0.2 (please do not use the term mixing factor, it is misleading) was this for Pratt or MSR1? A change from 0.2 to 0.15 with MSR1 will not matter much. 2011/12/12 shamik chakrabarti shamikphy at gmail.com mailto:shamikphy at gmail.com: Dear Dr Peter Blaha and Dr Pascal, The material is a ferrimagnetic transition metal compound and a charge transfer insulator and the gap is between d and O p states. Yes we have started MBJ potential calculation from the converged GGA charge density. So what we can do, we can start from the scratch with MBJ potential and after few iterations will get shifted to MSR1 mixing to improve the convergence. We hope that will help. Thank you for all your helps. with regards, On Mon, Dec 12, 2011 at 1:31 PM, pascal boulet pascal.boulet at univ-provence.fr mailto:pascal.boulet at univ-provence.fr wrote: Dear Dr. Chakrabarti, All right. So, another idea: could it be that you restarted your m-BJ calculation using the converged GGA or GGA+U density? I ran into these kinds of troubles several times. I found it preferable to start from scratch... Hope this help, Pascal On 12/12/2011 08:45, shamik chakrabarti wrote: Dear Dr. Pascal, As we were getting Ghost band error due to large charge fluctuation during initial cycle *we have reduced the mixing parameter from 0.2 to 0.15 hence thereafter we have not received ghost band error yet.* As long as variation of RMT is concerned the
[Wien] w2web: interactive/background
Hello, I've configured the batch option in w2web so that the jobs only start when at least one CPU is free. However, users can still choose interactive or background in the run_scf menu. Is there a way to deactivate these two possibilities, or do I have to trust all users to patiently stand in line? Thank you, Holger
