Re: [Wien] the error of semicore band ranges too large and NMR calculations
Hi Peter, Many thanks for the clarifications! The Rmt for Ca is 2.25 while 0.65 for H, such a difference is way too large? anyways, I will do as you suggested. Best wishes, Bing PS: I attach the STRUCT file for your information. On Thu, 12/5/13, Peter Blaha pbl...@theochem.tuwien.ac.at wrote: Subject: Re: [Wien] the error of semicore band ranges too large and NMR calculations To: A Mailing list for WIEN2k users wien@zeus.theochem.tuwien.ac.at Received: Thursday, December 5, 2013, 2:04 AM This new test (v 13.1) checks for ghostbands, which otherwise would go through without notice. I consider it a VERY important check and in almost all cases it is a severe problem. It has the same origin as the STOP due to QTL-B too large, namely unphysical ghostbands. Ghostbands occure for two reasons: a) the energy parameters are not set properly. This means most of the time that the wien2k-defaults for your system (mainly due to the required RMT values or due to a particular charge transfer) are not good. In most cases it comes because for ONE atoms there are 2 expansion energies for the same l, and these energies are too close. b) The sphere sizes are too different. This happens in particular when a cation (like your Na or Ca) has too large spheres compared to H, O, B. Often such ghostbands appear for (partly) converged calculations. Thus for your case, I suggest you reduce your large spheres (Na, Ca ??) by eg. 0.3 bohr (I can't be more specific since I don't know any details). Am 05.12.2013 06:51, schrieb Bing Zhou: Dear all, LAPW2: semicore band-ranges too large, possible ghost band occurred at the 15th SCF for the mineral ulexite (NaCa[B5O7(OH)4]H2O), so my question is: does such an error will affect the NMR calculations for this mineral? Best wishes, Bing On Wed, 12/4/13, t...@theochem.tuwien.ac.at t...@theochem.tuwien.ac.at wrote: Subject: Re: [Wien] semicore band ranges too large error To: A Mailing list for WIEN2k users wien@zeus.theochem.tuwien.ac.at Received: Wednesday, December 4, 2013, 3:08 PM This check was introduced recently to detect ghost bands. If this problem appears at the very beginning of the SCF iteration for a new geometry then there is probably no problem of ghost bands. This is just the starting density which is not good. To avoid the stop of the calculation, in case.in2 set the value of iqtlsave to 0. F. Tran On Wed, 4 Dec 2013, Torsten Weissbach wrote: Dear all, after switching to Wien2k_13, I frequently get the semicore band ranges too large error, often during relaxation. Though I can understand why that should not happen, can you explain what could have gone wrong that it appears and how the source of this error can be traced? Best regards, Torsten ___ 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 ___ 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.htmlUlexite P 402_P-1 RELA 16.659832 24.320785 12.619596 90.36109.05104.98 ATOM -1: X=0.14142709 Y=0.02661075 Z=0.30475395 MULT= 2 ISPLIT= 8 -1: X=0.85857291 Y=0.97338925 Z=0.69524605 Ca NPT= 781 R0=0.0001 RMT= 2.25 Z: 20.0 LOCAL ROT MATRIX:1.000 0.000 0.000
[Wien] Slab symmetry with SOC
Dear WIEN2k experts, I am calculating 29-atom Fe(001) slab with SOC with easy axis along [100]. Without SOC one can find more symmetries, and one has only 15 inequivalent atoms. However, when performing the calculation with such slab the results are different compared to the complex calculation with pure slab of 29 atoms. I believe that the correct result in this calculation is that surface bands along [100] and [-100] are the same, and bands along [010] and [0-10] are different. So one should have 3 slightly different set of surface bands: along [100] (identical to [-100]), [010], and [0-10]. Of course on the opposite surfaces of the slab things will have the inversion symmetry. I believe that one of the programs, e.g. symmetso should in principle be able to find out, whether the symmetries are correct or not, and produce the correct struct file, which is possibly a bit more symmetric than the original file. Please advise. Regards, Lukasz ___ 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
Re: [Wien] berryphase
Dear Shahrbano, ... Although we could reproduce the SP of the sample, P_s= P_z(lambda1)- P_z(lambda0) = 0.312113863793- 1.52399256575e-11 = 0.31211386360 C/m^2 which is very close to the readme file (but not exactly the same as it P_s= P_z(lambda1)- P_z(lambda0)= 0.31140111708550217-1.4486341471349937e-11= 0.3114011170710158 C/m^2), there are some things which are not clear for us. This difference is not material. Tutorials were done with an earlier version of Wien2k and a default SCF convergence. Possibly, a tighter convergence will lead to the same result in both cases. Why would not define the P_s just as P_z(lambda1)? In general, P(lambda0) = 0 may not always be true due to pi rapping. So it will be a very slippery assumption. This is why I would insist on doing both calculations (lambda0, lambda1) even though you might expect zero. We examined these two structures by calculating the exerted forces on the atoms of them to check whether they are in their relaxed positions or not. We found that the displaced atoms in lambda1.strcut were under tension--:FOR002 and :FGL002 are not zero. Are there total or partial forces? What are the values? In the way as discussed in tutorial1, the SP certainly will depend on the displacements. If we increase the amount of displacement, then we will obtain larger SP. In any case, you are need a well converged atomic positions. In our calculations we try to optimize structure to better than 2 mRy/Bohr. (Sheikh can probably comment more.) So, unlike Boron effective charge calculations it appears that the SP calculations cannot give a unique result? Indeed, the SP should be unique. There should be only one well converged structure. Of course, it will be sensitive to the choice of XC functional. 3) And, why we should not fully initialize the centrosymmetric one? We do not want Wien2k to realize its higher symmetry. Therefore, the initialization is done for low-symmetry lambda1 case only. Both structures should have identical symmetry operations in order to ensure consistency and comparability of the results. In summary, according to the definition of SP, a transient from a centrosymmetry to a noncentrosymmetry seems to be necessary. But, here both of the phases are tetragonal, while in the paper one of them is considered to be cubic. Strictly speaking, you are right. We would need a cubic structure for lambda0 and you can try it. What you will find in this case that it does not matter for P(lambda0). Where is the transition in this tutorial? You can make a transition by choosing an intermediate structure (say lambda05). I am not aware of unique way to define the intermediate state: we know for sure only lambda0 and lambda1. But you can imagine lambda1 as a distorted case of lambda0. For lambda05 you need half of the distortions. Of course, NO optimization of atomic positions should be performed for lambda05. Otherwise you will end up with lambda1 again. What will be the criterion to move up the atoms? Zero force and stress for lambda1. What is the difference between SP and total polarization? It is the essence of the modern polarization theory that the total polarization does not make sense. Only a difference matters, i.e. SP. Would you discuss how we can find the centrosymmetric and noncentrosymmetric ones for any cases? This part I am not sure, especially for GaN. The thinking should start with analysis of measurable quantities/effects, which you would like to model. Thank you Oleg ___ 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
Re: [Wien] berryphase
Hello Shahrbano, I also agree with Dr. Rubel that this fraction of discrepancy that you are getting is probably due to the fact we made this tutorial on Wien2k version 11.0. Regarding the forces for optimizing the structure, I always try to optimize my structure to a much lower value (0.2 mRy/bohr) of forces. However, this doesn't make much of a difference to the final result though. Compared to the optimized structure with default force tolerance (2 mRy/bohr), the atomic positions varies only in fourth or fifth decimal places which might change your polarization by 0.1 to 1 % (like you are getting). This is negligible if you are consistent when comparing properties between two calculations. Either use 2 mRy/bohr for both the cases or 0.2 mRy/bohr. Also you can try to understand more about modern theory of polarization from here http://www.physics.rutgers.edu/~dhv/pubs/local_preprint/dv_fchap.pdf Hope that helps. Sheikh On Thu, Dec 5, 2013 at 11:56 AM, Oleg Rubel oru...@lakeheadu.ca wrote: Dear Shahrbano, ... Although we could reproduce the SP of the sample, P_s= P_z(lambda1)- P_z(lambda0) = 0.312113863793- 1.52399256575e-11 = 0.31211386360 C/m^2 which is very close to the readme file (but not exactly the same as it P_s= P_z(lambda1)- P_z(lambda0)= 0.31140111708550217-1.4486341471349937e-11= 0.3114011170710158 C/m^2), there are some things which are not clear for us. This difference is not material. Tutorials were done with an earlier version of Wien2k and a default SCF convergence. Possibly, a tighter convergence will lead to the same result in both cases. Why would not define the P_s just as P_z(lambda1)? In general, P(lambda0) = 0 may not always be true due to pi rapping. So it will be a very slippery assumption. This is why I would insist on doing both calculations (lambda0, lambda1) even though you might expect zero. We examined these two structures by calculating the exerted forces on the atoms of them to check whether they are in their relaxed positions or not. We found that the displaced atoms in lambda1.strcut were under tension--:FOR002 and :FGL002 are not zero. Are there total or partial forces? What are the values? In the way as discussed in tutorial1, the SP certainly will depend on the displacements. If we increase the amount of displacement, then we will obtain larger SP. In any case, you are need a well converged atomic positions. In our calculations we try to optimize structure to better than 2 mRy/Bohr. (Sheikh can probably comment more.) So, unlike Boron effective charge calculations it appears that the SP calculations cannot give a unique result? Indeed, the SP should be unique. There should be only one well converged structure. Of course, it will be sensitive to the choice of XC functional. 3) And, why we should not fully initialize the centrosymmetric one? We do not want Wien2k to realize its higher symmetry. Therefore, the initialization is done for low-symmetry lambda1 case only. Both structures should have identical symmetry operations in order to ensure consistency and comparability of the results. In summary, according to the definition of SP, a transient from a centrosymmetry to a noncentrosymmetry seems to be necessary. But, here both of the phases are tetragonal, while in the paper one of them is considered to be cubic. Strictly speaking, you are right. We would need a cubic structure for lambda0 and you can try it. What you will find in this case that it does not matter for P(lambda0). Where is the transition in this tutorial? You can make a transition by choosing an intermediate structure (say lambda05). I am not aware of unique way to define the intermediate state: we know for sure only lambda0 and lambda1. But you can imagine lambda1 as a distorted case of lambda0. For lambda05 you need half of the distortions. Of course, NO optimization of atomic positions should be performed for lambda05. Otherwise you will end up with lambda1 again. What will be the criterion to move up the atoms? Zero force and stress for lambda1. What is the difference between SP and total polarization? It is the essence of the modern polarization theory that the total polarization does not make sense. Only a difference matters, i.e. SP. Would you discuss how we can find the centrosymmetric and noncentrosymmetric ones for any cases? This part I am not sure, especially for GaN. The thinking should start with analysis of measurable quantities/effects, which you would like to model. Thank you Oleg ___ 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
