Dear Laurence Marks Sir, Thank you very much for your response. I have understood what you want to say.
with best regards, 2011/9/5 Laurence Marks <L-marks at northwestern.edu> > Check the confidence levl, e.g. t-test (i am not an expert with this > package). Xrd Reitfeld is as susceptible to GIGO as DFT. > On Sep 5, 2011 11:58 AM, "shamik chakrabarti" <shamikphy at gmail.com> wrote: > > Dear Laurence Marks Sir, > > > > Yes this is an oxide and it is an insulator and probably I have made it > > a metal by creating *cationic vacancies*. Sir I will let you know the > detail > > after checking it from case.output2. But Sir, please forgive my > curiosity, I > > could not wait to ask you and also going a bit away from wien2k > questions: > > 1) Sir the goodness of fit (GOF) obtained from Rietveld analysis done > > through XPERT Highscore plus : 1.0038 > > and except this data we do not have any other proof to show that it > > really have cationic vacancies. > > Then Sir according to you we can not trust this data (considering GOF) > > only to consider cationic vacancies? > > > > With best regards, > > > > > > > > On Mon, Sep 5, 2011 at 9:31 PM, Laurence Marks <L-marks at northwestern.edu > >wrote: > > > >> Follow the science, not the DFT. > >> > >> 1) Unless you have a large grain size and synchotron data I really > >> wonder about the logic of removing 1 atom in a 2x1x1 supercell. > >> Particularly if this is an oxide, have you made it a metal whereas it > >> should be an insulator? Does the fit pass significance tests etc? Do > >> you have other data that implies vacancies? > >> 2) In terms of the DFT, I expect that you have made it a metal which > >> is harder to converge than an insulator. Check in case.output2 in both > >> cases (a quick, pseudo DOOS). If it really does have vacancies, you > >> might need more than 7 kpts, and I suggest using TEMPS. > >> > >> 2011/9/5 shamik chakrabarti <shamikphy at gmail.com>: > >> > Dear wien2k users, > >> > I have performed a 56 atom / unit cell calculation for a > >> > ferrimagnetic material. It was well converged both in energy and > charge > >> by > >> > 60 iterations. 14 K points were used for this calculation. Then I have > >> > generated a 2x1x1 supercell having 112 atoms / supercell. This was > done > >> to > >> > achieve better experimental model as obtained through Rietveld > analysis. > >> > From Rietveld analysis it was also seen that for 112 atoms we can > >> consider a > >> > cation (Fe) vacancy and we have generated it by deleting one Fe atom > from > >> > the supercell. Final structure, hence, contains 111 atoms and all > other > >> > occupancies at different lattice sites are well matched with Rietveld > >> > analysis of experimental XRD. I am using 2 k points for this 111 atom > >> > supercell. But even after 60 iterations the convergence achieved are > as > >> > follows: > >> > cc: 0.234... cc was set to 0.001 > >> > ec: 0.063... ec was set to 0.0001 > >> > Sir, my question are: > >> > 1) As the supercell is merely an extension of the 56 atoms unit cell > with > >> > more accurate values of atomic occupancies as in the experimental > >> structure, > >> > why it should at all taking so much time to converge? > >> > 2) We have created one defect by creating a Fe vacancy...is it that > the > >> > structures having defect take more time to converge?...but as far as > our > >> > analysis until now..the structure should have one Fe vacancy per 112 > >> > atoms... > >> > 3) As we have obtained converged solutions for 56 atom cell by using > 14 k > >> > points..is it that we should use 7K points for 111 atom supercell > >> > calculation?..is 2 K points are actually small in order to achieve > >> > convergence of this structure? > >> > 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 > >> > > >> > _______________________________________________ > >> > Wien mailing list > >> > Wien at zeus.theochem.tuwien.ac.at > >> > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > >> > > >> > > >> > >> > >> > >> -- > >> Laurence Marks > >> Department of Materials Science and Engineering > >> MSE Rm 2036 Cook Hall > >> 2220 N Campus Drive > >> Northwestern University > >> Evanston, IL 60208, USA > >> Tel: (847) 491-3996 Fax: (847) 491-7820 > >> email: L-marks at northwestern dot edu > >> Web: www.numis.northwestern.edu > >> 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 > > _______________________________________________ > 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... 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