<p>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.</p>
<div class="gmail_quote">On Sep 5, 2011 11:58 AM, "shamik chakrabarti" <<a href="mailto:shamikphy@gmail.com">shamikphy@gmail.com</a>> wrote:<br type="attribution">> Dear Laurence Marks Sir,<br>> <br>
> Yes this is an oxide and it is an insulator and probably I have made it<br>> a metal by creating *cationic vacancies*. Sir I will let you know the detail<br>> after checking it from case.output2. But Sir, please forgive my curiosity, I<br>
> could not wait to ask you and also going a bit away from wien2k questions:<br>> 1) Sir the goodness of fit (GOF) obtained from Rietveld analysis done<br>> through XPERT Highscore plus : 1.0038<br>> and except this data we do not have any other proof to show that it<br>
> really have cationic vacancies.<br>> Then Sir according to you we can not trust this data (considering GOF)<br>> only to consider cationic vacancies?<br>> <br>> With best regards,<br>> <br>> <br>
> <br>> On Mon, Sep 5, 2011 at 9:31 PM, Laurence Marks <<a href="mailto:L-marks@northwestern.edu">L-marks@northwestern.edu</a>>wrote:<br>> <br>>> Follow the science, not the DFT.<br>>><br>>> 1) Unless you have a large grain size and synchotron data I really<br>
>> wonder about the logic of removing 1 atom in a 2x1x1 supercell.<br>>> Particularly if this is an oxide, have you made it a metal whereas it<br>>> should be an insulator? Does the fit pass significance tests etc? Do<br>
>> you have other data that implies vacancies?<br>>> 2) In terms of the DFT, I expect that you have made it a metal which<br>>> is harder to converge than an insulator. Check in case.output2 in both<br>>> cases (a quick, pseudo DOOS). If it really does have vacancies, you<br>
>> might need more than 7 kpts, and I suggest using TEMPS.<br>>><br>>> 2011/9/5 shamik chakrabarti <<a href="mailto:shamikphy@gmail.com">shamikphy@gmail.com</a>>:<br>>> > Dear wien2k users,<br>
>> > I have performed a 56 atom / unit cell calculation for a<br>>> > ferrimagnetic material. It was well converged both in energy and charge<br>>> by<br>>> > 60 iterations. 14 K points were used for this calculation. Then I have<br>
>> > generated a 2x1x1 supercell having 112 atoms / supercell. This was done<br>>> to<br>>> > achieve better experimental model as obtained through Rietveld analysis.<br>>> > From Rietveld analysis it was also seen that for 112 atoms we can<br>
>> consider a<br>>> > cation (Fe) vacancy and we have generated it by deleting one Fe atom from<br>>> > the supercell. Final structure, hence, contains 111 atoms and all other<br>>> > occupancies at different lattice sites are well matched with Rietveld<br>
>> > analysis of experimental XRD. I am using 2 k points for this 111 atom<br>>> > supercell. But even after 60 iterations the convergence achieved are as<br>>> > follows:<br>>> > cc: 0.234... cc was set to 0.001<br>
>> > ec: 0.063... ec was set to 0.0001<br>>> > Sir, my question are:<br>>> > 1) As the supercell is merely an extension of the 56 atoms unit cell with<br>>> > more accurate values of atomic occupancies as in the experimental<br>
>> structure,<br>>> > why it should at all taking so much time to converge?<br>>> > 2) We have created one defect by creating a Fe vacancy...is it that the<br>>> > structures having defect take more time to converge?...but as far as our<br>
>> > analysis until now..the structure should have one Fe vacancy per 112<br>>> > atoms...<br>>> > 3) As we have obtained converged solutions for 56 atom cell by using 14 k<br>>> > points..is it that we should use 7K points for 111 atom supercell<br>
>> > calculation?..is 2 K points are actually small in order to achieve<br>>> > convergence of this structure?<br>>> > Any response in this regard will be very helpful for us. Thanks in<br>>> advance.<br>
>> > with regards,<br>>> ><br>>> > --<br>>> > Shamik Chakrabarti<br>>> > Senior Research Fellow<br>>> > Dept. of Physics & Meteorology<br>>> > Material Processing & Solid State Ionics Lab<br>
>> > IIT Kharagpur<br>>> > Kharagpur 721302<br>>> > INDIA<br>>> ><br>>> > _______________________________________________<br>>> > Wien mailing list<br>>> > <a href="mailto:Wien@zeus.theochem.tuwien.ac.at">Wien@zeus.theochem.tuwien.ac.at</a><br>
>> > <a href="http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien">http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien</a><br>>> ><br>>> ><br>>><br>>><br>>><br>>> --<br>
>> Laurence Marks<br>>> Department of Materials Science and Engineering<br>>> MSE Rm 2036 Cook Hall<br>>> 2220 N Campus Drive<br>>> Northwestern University<br>>> Evanston, IL 60208, USA<br>
>> Tel: (847) 491-3996 Fax: (847) 491-7820<br>>> email: L-marks at northwestern dot edu<br>>> Web: <a href="http://www.numis.northwestern.edu">www.numis.northwestern.edu</a><br>>> Research is to see what everybody else has seen, and to think what<br>
>> nobody else has thought<br>>> Albert Szent-Gyorgi<br>>> _______________________________________________<br>>> Wien mailing list<br>>> <a href="mailto:Wien@zeus.theochem.tuwien.ac.at">Wien@zeus.theochem.tuwien.ac.at</a><br>
>> <a href="http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien">http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien</a><br>>><br>> <br>> <br>> <br>> -- <br>> Shamik Chakrabarti<br>> Senior Research Fellow<br>
> Dept. of Physics & Meteorology<br>> Material Processing & Solid State Ionics Lab<br>> IIT Kharagpur<br>> Kharagpur 721302<br>> INDIA<br></div>