Make sure the Na sphere is not too big ! Eventually, use the same sphere as for Nb. Otherwise use "defaults". Such simple system should converge very easily.
jadhikari at clarku.edu schrieb: > Dear Wien2k users, > > Thank you very much for the suggestion for my question on ionic versus > covalent systems. > > I have tried with mixing parameter of 0.1 most of the time and changed it > to 0.05 or 0.2 or 0.25 or 0.4 when things do not work. As for example, > NaNbO3- > > 1. Most of the time I get ghost bands which is corrected by changing the > energies in the case.in1 file and changing the global energy parameter > based on the :FER energy. I have tried adding local orbitals and changed > its energy until the ghost bands are gone. Energies are used based on the > DOS plot rather than putting something inaccurate or wild. > > The term ghost band I mean is when QTL-B value is higher than 5.00. There > are other ionic systems in which I could manage to go below 5.00 and the > system showed no error. The minimum that I got was 2.10 and never it went > below this value. I tried more than 100 times to fix this. So, moving up > in k-points with this QTL-B value is not appropriate as the calculation > surely shows the ghost band with higher QTL-B value. > > 2. RMT for the three atoms are optimized. Values are chosen so that there > is very very small leackage of charges. It has two extreme values- the > minimum RMT is the one in which the calculation is stuck at lapw2 and the > maximum is the one in which there is a nearest neighbor error. Value in > between these two with negligible leakage and close to that of other atoms > is the optimized RMT. (UG's specification is also followed) > > 3. RKmax is altered from 4.00 to 7.00. I got the system to converg with > 5.50 and not with other ones. There is no basis for its optimization as I > am aware of (considering the no of plane waves required to accurately > describe the system). Maybe the output changes with 6.00 or 6.50 or 7.00. > So convergence with respect to RKmax is still under investigation. EFG > seems to be extremely sensitive to even a slight change. > > 4. No of points in the irreducible brillouin zone is started with the > minimum. Then, it is increased to the next higher one possible based on > the symmetry of the system generated by "x kgen". Now the problem comes. > Either the RMT has to be changed or ghost band has to be fixed....... > > 5. The TEMP smearing of 0.002 Ry was found to produce no errors in most of > the cases. I have tested this with other methods and different values. > > 6. PBE-XC functional is the one chosen to be more accurate than LDA-XC for > the present case. But I have tried both. > > 7. s and p orbitals receive 0 and d receives 1 for LAPW and APW+lo > respectively. Other combinations did not seem to be right. The energy > window is -10.0 to 2.0 and the values upto -12.0 for minimum and upto 3.0 > for maximum have also been tried. > > Hence, this ionic system needs something that I have not understood yet. I > have thought of the following now, > > 1. Lowering the space group symmetry or > 2. Using supercells or > 3. Using all the system's default parameters or > 4. ........ > > Any suggestion would be highly appreciated. > > Once again thanking you. > > Subin Adhikari > > > > > > > > Dear Subin, >> You can change the parameter in case.inm from the default 0.40 to 0.01, > as > % > > > > _______________________________________________ > Wien mailing list > Wien at zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien -- P.Blaha -------------------------------------------------------------------------- Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna Phone: +43-1-58801-15671 FAX: +43-1-58801-15698 Email: blaha at theochem.tuwien.ac.at WWW: http://info.tuwien.ac.at/theochem/ --------------------------------------------------------------------------