<div dir="ltr">Dear Prof. Tran and Prof. Blaha,<br><div><br></div><div> Thank you for your elaborate response. I got the point.</div><div><br></div><div>Thanks once again.</div><div><br></div><div>with regards,</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sun, 8 Mar 2020 at 16:10, Peter Blaha <<a href="mailto:pblaha@theochem.tuwien.ac.at">pblaha@theochem.tuwien.ac.at</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">It really depends on the specific example if you need to be carefully <br>
with the starting point, since both, LDA+U and mBJ can give multiple <br>
solutions in certain cases.<br>
<br>
Eg: MnO or NiO do not require any special care. The dominant cubic <br>
crystal field is sufficient to drive the correct solution and both, <br>
GGA+U and mBJ will give only one solution, independent on the starting <br>
conditions.<br>
<br>
Very different is eg. FeO: Both, GGA+U and in particular mBJ will NOT <br>
give a band gap when started with plain GGA (and probably also not when <br>
starting from scratch using atomic densities ??)<br>
<br>
An analysis of the partial Fe-DOS is necessary, followed with a <br>
reoccupation of the density matrix by hand to occupy the proper single <br>
orbital. Using this starting dmat-files, GGA+U gives an insulator (and <br>
this solution should have lower energy - depending on U). Continuation <br>
with mBJ from such a solution, also gives a nice band gap.<br>
<br>
Analyse your partial TM-d state DOS !<br>
<br>
Am 08.03.2020 um 11:25 schrieb Tran, Fabien:<br>
> Hi,<br>
> <br>
> It is recommended (but not mandatory) to do first a GGA calculation <br>
> before using GGA+U or mBJ. By doing so, the starting electron density <br>
> for the GGA+U/mBJ SCF iterations may be better than the one <br>
> from init_lapw (lstart/dstart) in order to reduce the number of <br>
> iterations and/or to reach the proper ground state.<br>
> <br>
> It may also be a good idea (but again not mandatory) to start a mBJ <br>
> calculation using the GGA+U electron density.<br>
> <br>
> FT<br>
> <br>
> ------------------------------------------------------------------------<br>
> *From:* Wien <<a href="mailto:wien-bounces@zeus.theochem.tuwien.ac.at" target="_blank">wien-bounces@zeus.theochem.tuwien.ac.at</a>> on behalf of <br>
> shamik chakrabarti <<a href="mailto:shamik15041981@gmail.com" target="_blank">shamik15041981@gmail.com</a>><br>
> *Sent:* Sunday, March 8, 2020 10:09 AM<br>
> *To:* A Mailing list for WIEN2k users<br>
> *Subject:* [Wien] confusion with GGA+U and mbj<br>
> Dear Wien2k users,<br>
> <br>
> If simulation of a material is to run with <br>
> GGA+U to get an approximate band gap, then *whether GGA+U or GGA* has to <br>
> run as a first step for running mbj?<br>
> <br>
> As user guide says that we have to run a normal SCF prior to mbj, my <br>
> confusion is whether the normal SCF is to run with GGA or GGA+U if U is <br>
> mandatory for the material.<br>
> <br>
> Looking forward to your response in this regard.<br>
> <br>
> with regards,<br>
> <br>
> -- <br>
> Dr. Shamik Chakrabarti<br>
> Research Fellow<br>
> Department of Physics<br>
> Indian Institute of Technology Patna<br>
> Bihta-801103<br>
> Patna<br>
> Bihar, India<br>
> <br>
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> <br>
<br>
-- <br>
--------------------------------------------------------------------------<br>
Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna<br>
Phone: +43-1-58801-165300 FAX: +43-1-58801-165982<br>
Email: <a href="mailto:blaha@theochem.tuwien.ac.at" target="_blank">blaha@theochem.tuwien.ac.at</a> WIEN2k: <a href="http://www.wien2k.at" rel="noreferrer" target="_blank">http://www.wien2k.at</a><br>
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</blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div style="font-size:small">Dr. Shamik Chakrabarti</div><div style="font-size:small">Research Fellow </div><div style="font-size:small">Department of Physics</div><div style="font-size:small">Indian Institute of Technology Patna</div><div style="font-size:small">Bihta-801103</div><div style="font-size:small">Patna</div><div style="font-size:small">Bihar, India</div></div></div></div></div></div></div></div>