<html dir=""><head><style id="axi-htmleditor-style" type="text/css">p { margin: 0px; }</style></head><body style="font-size: 10pt; font-family: Arial; background-image: none; background-repeat: repeat; background-attachment: fixed;">Dear Giuseppe,<br><br>Many thanks for your quick response. As you have correctly guessed, the system is an organic material (fluorinated graphene). From U=0 to 3.4, M is increasing gradually up to the expected value, M remains constant till U=3.6 eV, then by increasing U, again M is reduced very soon to zero. Is this what one expected always from +U calculations, when goes up further from the optimum U value? From your answer, it is concluded to be a strange behavior due to the organic nature of this material.<br><div class="x-axi-signature"><br><div class="x-axi-signature" style="; font-size: 10pt; font-family: Arial;">Best regards,<div><br></div><div>F. Marsusi,<br><br>Amirkabir University of Technology.</div></div></div><br>On Fri, 02/10/2017 08:09 PM, Giuseppe Mattioli <giuseppe.mattioli@ism.cnr.it> wrote:<br><blockquote style="border-left: 2px solid rgb(00, 00, 204); padding-left: 4px; margin-left: 16px;"><div style="font-family: Arial; font-size: 10pt;">Dear F. Marsusi<br>First of all you are not providing any detail of your system, so we cannot even guess what is "natural" for it.<br>However, you are using the Hubbard U correction in a semiempirical way, and there is therefore no way to choose the U value but that reproducing some <br>measured parameter, and not very much to do if unexpected or strange results appear at a given (unphysical?, problematic?) U value.<br>In my experience the application of U to organic molecules has been always problematic due to the strong hybridization between C 2s and C 2p orbitals, <br>and to the application of the correction to 2p orbitals only.<br>HTH<br><div align="left">Giuseppe<br></div><br>On Friday, February 10, 2017 07:25:10 PM FARAH MARSUSI wrote:<br>> Dear all,<br>> <br>> By GGA+U as implemented in QE, the correct magnetization (M) and band gap was obtained. The correct U value for each atom was obtained by intensive<br>> step by step runs to reach gradually the experimental M value, and therefore band gap. All results are OK till now (the U value itself also= 3.4 eV<br>> for carbon and fluorine is acceptable ). However, by enlarging the obtained U value a bit (to 3.7 eV), the predicted M come back to that of pure<br>> GGA. Is it natural, or a problem exist?<br>> <br>> <br>> Best regards,<br>> F. Marsusi,<br><br>********************************************************<br>- Article premier - Les hommes naissent et demeurent<br>libres et égaux en droits. Les distinctions sociales<br>ne peuvent être fondées que sur l'utilité commune<br>- Article 2 - Le but de toute association politique<br>est la conservation des droits naturels et <br>imprescriptibles de l'homme. Ces droits sont la liberté,<br>la propriété, la sûreté et la résistance à l'oppression.<br>********************************************************<br><br> Giuseppe Mattioli <br> CNR - ISTITUTO DI STRUTTURA DELLA MATERIA <br> v. Salaria Km 29,300 - C.P. 10 <br> I 00015 - Monterotondo Stazione (RM), Italy <br> Tel + 39 06 90672342 - Fax +39 06 90672316 <br> E-mail: <a href="mailto:<giuseppe.mattioli@ism.cnr.it>" target="_blank"><giuseppe.mattioli@ism.cnr.it></a><br> <a href="http://www.ism.cnr.it/en/staff/giuseppe-mattioli/" target="_blank">http://www.ism.cnr.it/en/staff/giuseppe-mattioli/</a><br> ResearcherID: F-6308-2012<br><br>_______________________________________________<br>Pw_forum mailing list<br><a href="mailto:Pw_forum@pwscf.org" target="_blank">Pw_forum@pwscf.org</a><br><a href="http://pwscf.org/mailman/listinfo/pw_forum" target="_blank">http://pwscf.org/mailman/listinfo/pw_forum</a><br><br><font color="#999999">--<br>This email was Anti Virus checked by Astaro Security Gateway. <a href="http://www.sophos.com" target="_blank">http://www.sophos.com</a><br></font></div></blockquote></body></html>