[Wien] Different Rmt's for atoms of one type

Thu Apr 21 17:39:55 CEST 2011

No, SRC_RMTCheck (search for RMTCheck). If you cannot find it, let me
know -- I have to teach in a few minutes...

2011/4/21 Maxim Rakitin <rms85 at physics.susu.ac.ru>:
> Thank you Laurence and Evgenia,
>
> Laurence, do you mean x_lapw script which attached to 2 emails in the
> mailing list?
> 1) [Wien] severe bug in x_lapw by Peter Blaha on 22.06.2010 2:03.
> 2) Re: [Wien] LAPW2 crashed in parallel mode by Peter Blaha on 01.07.2010
> 16:09.
>
> Thanks a lot for your help.
> Maxim
>
> 21.04.2011 19:57, Евгения Каблиман пишет:
>
> Maxim, perhaps, you are interesting in calculation of the formation
> energies.
> And therefore, I am personally not sure, how is then better (and correct) to
> estimate this value when Fe atoms have different RMT's in one supercell.
> As Laurence very well explained, when "you use different RMTs for the Fe in
> effect you make them different".
>
> 2011/4/21 Laurence Marks <L-marks at northwestern.edu>
>>
>> An approximate explanation, but first a caveat: dealing with small
>> RMT's in Wien2k is not completely trivial.
>>
>> In Wien2k you have two different basis sets, a radial grid + orbitals
>> inside the RMT, plane waves outside. If you use different RMTs for the
>> Fe in effect you make them different. For instance, try setting up a
>> Fe cell with two different RMTs (i.e. a supercell), converge it then
>> do aim. You will find that there has been a small charge transfer
>> between the Fe's, which will go to zero as you increase RKMAX.
>>
>> For your problem, I would go beyond setrmt (which is OK, but not
>> always optimal) and use a smaller RMT for the C (maybe 1.3) and
>> increase that for the Fe. You will have to do this by hand. Be careful
>> about going too small with the C as if you do you will lose core
>> charge (although .lcore helps); you also need to be careful about
>> losing core electrons from the Fe. In both cases look in case.outputm
>> to see how far the core integrals are from integers. Scale RKMAX so
>> RKMAX/min(RMT) is roughly the same (e.g. 3.5), although you need to
>> add a bit when you decrease the RMTs. Probably something like 5-6
>> should be good for your problem.
>>
>> How to chose the "right" RMTs? I don't have any great wisdom, others
>> might have. I tend to use RMTCheck (look in the mailing list, or I can
>> ask Peter to add it to the contributed software) and check that the
>> step in the gradients at the RMT for the different atoms are
>> comparable. In most cases this gives results similar to setrmt. In
>> principle you can also do calculations for different values with
>> RKMAX/min(RMT) fixed and look for the minimum energy -- the few times
>> I've done this the results are about the same. Another method would be
>> to try and balance the charge lost in the core integrals, which gives
>> a similar result.
>>
>> 2011/4/21 Maxim Rakitin <rms85 at physics.susu.ac.ru>:
>> > Thank you Evgenia,
>> >
>> > I've already seen that link, but I'd like to get information why it is
>> > not
>> > possible from physical point of view.
>> >
>> > Maxim
>> >
>> > 21.04.2011 16:53, Евгения Каблиман пишет:
>> >
>> > Dear Maxim,
>> >
>> > identical elements should have identical RMT's.
>> > This link might help you http://www.wien2k.at/reg_user/faq/rmt.html .
>> >
>> > 2011/4/21 Maxim Rakitin <rms85 at physics.susu.ac.ru>
>> >>
>> >> Dear WIEN2k community,
>> >>
>> >> Is it correct to perform calculations with different Rmt radii for
>> >> atoms
>> >> of one type, e.g. Fe?
>> >>
>> >> I need to calculate total energy of a systems containing one
>> >> interstitial
>> >> carbon atom in bcc iron matrix. Carbon has quite large MT-radius
>> >> comparing
>> >> with H atom, so StructGen sets Rmt(Fe) to 1.59 a.u. and Rmt(C) to 1.41
>> >> a.u.
>> >> for lattice constant 5.394 a.u. In some papers (C. Domain et al., PRB
>> >> 69,
>> >> 144112 (2004)) Rmt(C) is even large than I got (~1.6 a.u.) and Rmt(Fe)
>> >> is
>> >> also much larger (~2.4 a.u.). But if I use the radii from the article,
>> >> WIEN2k doesn't allow me to perform further procedures - nn gives me
>> >> information about overlapping spheres.
>> >>
>> >> Can I use Rmt(Fe)=2.4 a.u. in all volume of my supercell except of the
>> >> nearest iron atoms?
>> >>
>> >> Thanks in advance for your answers.
>> >>
>> >> --
>> >> Best regards,
>> >>   Maxim Rakitin
>> >>   South Ural State University
>> >>   Chelyabinsk, Russia
>> >>   email: rms85 at physics.susu.ac.ru
>> >>   web: http://www.susu.ac.ru
>> >>
>> >> _______________________________________________
>> >> Wien mailing list
>> >> Wien at zeus.theochem.tuwien.ac.at
>> >> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>> >
>> >
>> >
>> > --
>> > Evgeniya Kabliman.
>> > Insitute of Materials Chemistry         Vienna University of Technology
>> > Getreidemarkt 9/165-TC, A-1060 Vienna, Austria
>> > Tel: +43 1 58801 15674        Fax: +43 1 58801 15698
>> > evgeniya at theochem.tuwien.ac.at            http://www.imc.tuwien.ac.at
>> >
>> > _______________________________________________
>> > Wien mailing list
>> > Wien at zeus.theochem.tuwien.ac.at
>> > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>> >
>> > _______________________________________________
>> > Wien mailing list
>> > Wien at zeus.theochem.tuwien.ac.at
>> > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>> >
>> >
>>
>>
>>
>> --
>> Laurence Marks
>> Department of Materials Science and Engineering
>> MSE Rm 2036 Cook Hall
>> 2220 N Campus Drive
>> Northwestern University
>> Evanston, IL 60208, USA
>> Tel: (847) 491-3996 Fax: (847) 491-7820
>> email: L-marks at northwestern dot edu
>> Web: www.numis.northwestern.edu
>> Chair, Commission on Electron Crystallography of IUCR
>> www.numis.northwestern.edu/
>> Research is to see what everybody else has seen, and to think what
>> nobody else has thought
>> Albert Szent-Gyorgi
>> _______________________________________________
>> Wien mailing list
>> Wien at zeus.theochem.tuwien.ac.at
>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>
>
>
> --
> Evgeniya Kabliman.
> Insitute of Materials Chemistry         Vienna University of Technology
> Getreidemarkt 9/165-TC, A-1060 Vienna, Austria
> Tel: +43 1 58801 15674        Fax: +43 1 58801 15698
> evgeniya at theochem.tuwien.ac.at            http://www.imc.tuwien.ac.at
>
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>
>

-- 
Laurence Marks
Department of Materials Science and Engineering
MSE Rm 2036 Cook Hall
2220 N Campus Drive
Northwestern University
Evanston, IL 60208, USA
Tel: (847) 491-3996 Fax: (847) 491-7820
email: L-marks at northwestern dot edu
Web: www.numis.northwestern.edu
Chair, Commission on Electron Crystallography of IUCR
www.numis.northwestern.edu/
Research is to see what everybody else has seen, and to think what
nobody else has thought
Albert Szent-Gyorgi