<html><body><div>Yes, now it makes sense to me. </div><div>I will work on that right away. </div><div>Thank you very much. </div><div><pre style="font-family: Helvetica,Arial,sans-serif; font-size: 13px" _mce_style="font-family: Helvetica,Arial,sans-serif; font-size: 13px;">David Guzman M
Department of Physics & Astronomy
California State University-Los Angeles
(310)528-4841</pre></div><div><br>On Apr 06, 2011, at 08:27 AM, Peter Blaha <pblaha@theochem.tuwien.ac.at> wrote:<br><br></div><div><blockquote type="cite"><div class="msg-quote"><div class="_stretch">Exactly, this could be the explanation. (Sorry, I mixed LDA/PBE energies.<br>
<br>
However, the situation could also be wrong with PBE, because I'd expect<br>
that the mBJ magnetic moment is bigger than the PBE moment, and<br>
the PBE functional does "not like" these large moments, thus<br>
favors the non-magnetic solution.<br>
<br>
Still, do GGA+U for the total energies ...<br>
<br>
Am 06.04.2011 17:09, schrieb <a href="mailto:tran@theochem.tuwien.ac.at" _mce_href="mailto:tran@theochem.tuwien.ac.at">tran@theochem.tuwien.ac.at</a>:<br>
> Hello,<br>
><br>
> Actually, this is the LDA (and not PBE) exchange-correlation functional<br>
> which is used for the energy when MBJLDA is used for the potential<br>
> (option 28).<br>
><br>
> If you want PBE for the energy you have to replace<br>
><br>
> exu=2.d0*(exupls + eclsd)<br>
> exd=2.d0*(exdnls + eclsd)<br>
> by<br>
> exu=2.d0*(exuppb + ecpbe)<br>
> exd=2.d0*(exdnpb + ecpbe)<br>
><br>
> in the part of the subroutine vxclm2.f which concerns option 28.<br>
> Then you recompile the lapw0 package.<br>
> Maybe, the antiferromagnetic state will be the lowest again?<br>
><br>
> F. Tran<br>
><br>
> On Wed, 6 Apr 2011, davgumo wrote:<br>
><br>
>> Dr. Blaha, thank you very much for your comments.<br>
>> What is a bit confusing about my case is that my very first calculation with<br>
>> PBE identifies the ground state in some peculiar antiferromagnetic insulator<br>
>> (very small band gap though) this result was expected. Now when I try to<br>
>> improve the band gap by performing mBJ calcs, I find that this magnetic order<br>
>> which once I identified as the ground state is no longer lowest in energy. In<br>
>> fact, I found out that the nonmagnetic case is much lower in energy according<br>
>> to mBJ.<br>
>><br>
>> Once again, it was expected that the ground state would be found as an<br>
>> antiferromagnetic insulator as shown with PBE.<br>
>><br>
>> Do think that mBJ somehow has trouble determining the ground state for this<br>
>> crystal?<br>
>><br>
>> I appreciate so much your help and the time you devote to all the users.<br>
>><br>
>> By the way, we will soon have some experimental measurements about the band<br>
>> gap of this crystal, I hope the calculated mBJ band gap agrees with the<br>
>> experiment this would be very nice.<br>
>><br>
>> David Guzman M<br>
>> Department of Physics& Astronomy<br>
>> California State University-Los Angeles<br>
>> (310)528-4841<br>
>><br>
>> On Apr 05, 2011, at 10:42 PM, Peter Blaha<<a href="mailto:pblaha@theochem.tuwien.ac.at" _mce_href="mailto:pblaha@theochem.tuwien.ac.at">pblaha@theochem.tuwien.ac.at</a>><br>
>> wrote:<br>
>><br>
>> Clearly, mBJ is only a POTENTIAL, not an energy-functional.<br>
>> In fact, the mBJ option in WIEN2k uses the PBE-energy-functional, but<br>
>> of course with the electron density (and spin-density) corresponding<br>
>> to mBJ<br>
>><br>
>> The question whether you can trust the mBJ/PBE results more than the PBE/PBE<br>
>> results is not so easy to answer and may depend on the specific case.<br>
>><br>
>> If your compound belongs somehow to the cuprate-family (with CuO2 planes<br>
>> and a Cu2+ ios) and you should get a significant Cu-moment the chances are<br>
>> high<br>
>> that PBE does not get the correct groundstate (insulator ? magnetism ?), i.e.<br>
>> both the PBE-density and the PBE-energy are "wrong".<br>
>><br>
>> The mBJ-density should be more reliable in this case and maybe ??? the<br>
>> PBE-energy for such a density is "better".<br>
>><br>
>> At least I would "backup" the mBJ results by some LDA+U or hybrid-DFT<br>
>> calculations.<br>
>><br>
>> Am 06.04.2011 05:38, schrieb davgumo:<br>
>>> Dear Wien users and Dr. Blaha<br>
>>><br>
>>> I have been performing first-principles calculations on a recently<br>
>>> synthesized crystal structure CuZrTiO5.<br>
>>> This is a copper oxide the exhibits some potential to be a high Tc<br>
>>> superconductor under doping.<br>
>>><br>
>>> First I was interested in finding the ground state, which according to PBE<br>
>>> calculations turns out to be in some antiferromagnetic order. After this I<br>
>>> was interested in<br>
>>> using mBJ to calculate an accurate value for the band gap, so I performed<br>
>>> mBJ calculation on this antiferromagnetic order where I found the lowest<br>
>>> energy. Recently I<br>
>>> decided to run mBJ calculations on all the possible magnetic cases for this<br>
>>> crystal. To my big surprise when I checked the energies calculated with mBJ<br>
>>> the lowest energy is<br>
>>> not longer on the magnetic configuration I found the ground state to be<br>
>>> according to the PBE calculation.<br>
>>><br>
>>> My question is if mBJ calculations are meant only to improve the band gap<br>
>>> and will not provide the ground state of the system<br>
>>><br>
>>> I appreciate any comments, hints, critics, etc that can help me to figure<br>
>>> this out, and get a better understanding of the mBJ potential.<br>
>>><br>
>>> Thank you very much.<br>
>>><br>
>>> I can provide more details if this is not clear.<br>
>>><br>
>>> David Guzman M<br>
>>><br>
>>> Department of Physics& Astronomy<br>
>>> California State University-Los Angeles<br>
>>><br>
>>><br>
>>><br>
>>><br>
>>> _______________________________________________<br>
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>><br>
>> --<br>
>> -----------------------------------------<br>
>> Peter Blaha<br>
>> Inst. Materials Chemistry, TU Vienna<br>
>> Getreidemarkt 9, A-1060 Vienna, Austria<br>
>> Tel: +43-1-5880115671<br>
>> Fax: +43-1-5880115698<br>
>> email: <a href="mailto:pblaha@theochem.tuwien.ac.at" _mce_href="mailto:pblaha@theochem.tuwien.ac.at">pblaha@theochem.tuwien.ac.at</a><br>
>> -----------------------------------------<br>
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>><br>
>><br>
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-- <br>
<br>
P.Blaha<br>
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