<div dir="ltr"><div class="gmail_default" style="font-family:georgia,serif">Dear Wien2k users,</div><div class="gmail_default" style="font-family:georgia,serif"><br></div><div class="gmail_default" style="font-family:georgia,serif">Thank you for your feedback.</div><div class="gmail_default" style="font-family:georgia,serif"><br></div><div class="gmail_default" style="font-family:georgia,serif">If I got this right, I see that the optimization doesn't lead necessary to a good results and experimental data are there to evaluate the accuracy of the calculation method, and by that I mean the choice of parameters, potential, structure ...</div><div class="gmail_default" style="font-family:georgia,serif">The methodology depends also on the purpose of the calculation, and the properties we are looking for.<br></div><div class="gmail_default" style="font-family:georgia,serif"><br></div><div class="gmail_default" style="font-family:georgia,serif">However, given the large interval in which reside the lattice parameters provided by different papers, how to be quite sure we have chosen the correct structure or that is closest to reality. I am aware of the fact that this is a vague question given the variety of the different compounds but is there at least some indications visible before or after the SCF cycles that could help evaluate the credibility of the .struct file ?</div><div class="gmail_default" style="font-family:georgia,serif"> </div><div class="gmail_default" style="font-family:georgia,serif">Faithfully,</div><div class="gmail_default" style="font-family:georgia,serif"><br></div><div class="gmail_default" style="font-family:georgia,serif"><br></div></div><img src="https://my-email-signature.link/signature.gif?u=139409&e=8861079&v=2883a1fe35cf8ce1aa0c1c472fead27ca9aa2e48be482983dfaf2d2a375c0d0e" style="width:0;max-height:0;overflow:hidden"><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Jul 25, 2017 at 4:55 PM, Tristan de Boer <span dir="ltr"><<a href="mailto:tristan.deboer@usask.ca" target="_blank">tristan.deboer@usask.ca</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">You can find many papers that use either approach. I considered this somewhat tangentially in a paper on several semiconductor polymorphs that were synthesized under different pressures. [1] We collected x-ray absorption and emission spectra on thee polymorphs, and compared our spectra to those calculated using the PBE GGA functional for both relaxed and unrelaxed atom positions. We found that there was worse agreement with experiment using relaxed parameters compared to the experimental parameters, so at least for this case, using the experimental structure yields more correct results. I'm not sure how universal this is, and it may not apply as you move higher up the 'Jacob's ladder' of density functional approximations.<br>
Best Regards,<br>
Tristan<br>
<br>
[1] doi:10.1103/PhysRevB.93.155205<span class=""><br>
<br>
<br>
On 2017-07-24 6:27 AM, Chouaib AHMANI FERDI wrote:<br>
</span><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">
Greatings Wien users,<br>
<br>
I just want to ask if the experimental parameters (lattice parameters,<br>
internal parameter, atomic positions, ...) are already available for a<br>
certain compound, would it be better to run SCF cycle with them or to<br>
make preliminary relaxation and volume optimization and then perform SCF<br>
cycle using the calculated parameters.<br>
<br>
Faithfully,<br>
<br>
<br>
<br>
--<br>
AHMANI FERDI Chouaïb<br>
Ph.D Student in Material Science<br>
Ecole Normale Supérieure<br>
Mohammed V University, Rabat.<br>
Tel : +212 6 94 59 57 60<br>
<br>
<br>
<br>
<br></span><span class="">
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</div></div></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><font face="georgia, serif" style="background-color:rgb(255,255,255)" color="#0b5394">AHMANI FERDI Chouaïb</font></div><div dir="ltr"><font face="georgia, serif" style="background-color:rgb(255,255,255)" color="#0b5394">"Laboratoire Matériaux Nanomatériaux Nanomagnétisme </font></div><div dir="ltr"><font face="georgia, serif" style="background-color:rgb(255,255,255)" color="#0b5394"> et Enseignement des Sciences"<br></font></div><div dir="ltr"><font face="georgia, serif" style="background-color:rgb(255,255,255)" color="#0b5394">Ecole Normale Supérieure</font></div><div dir="ltr"><span style="background-color:rgb(255,255,255)"><font color="#0b5394"><font face="georgia, serif">Université Mohammed V, </font><span style="font-family:georgia,serif;font-size:12.8px">Rabat. </span></font></span></div><div dir="ltr"><div><span style="background-color:rgb(255,255,255)"><font color="#0b5394"><font face="georgia, serif">Tel : </font><font face="trebuchet ms, sans-serif">+212 6 94 59 57 60</font></font></span></div><div><span style="background-color:rgb(255,255,255)"><font color="#0b5394"><br></font></span></div><div><font face="trebuchet ms, sans-serif"><br></font></div></div></div></div></div></div></div></div></div></div></div>
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