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

Maxim Rakitin rms85 at physics.susu.ac.ru
Thu Apr 21 17:18:09 CEST 2011


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 
> <mailto: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
>     <mailto: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
>     <mailto: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 <mailto:rms85 at physics.susu.ac.ru>
>     >>   web: http://www.susu.ac.ru
>     >>
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>     >
>     >
>     >
>     > --
>     > 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
>     <mailto:evgeniya at theochem.tuwien.ac.at> http://www.imc.tuwien.ac.at
>     >
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>     >
>
>
>
>     --
>     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 <http://www.numis.northwestern.edu>
>     Chair, Commission on Electron Crystallography of IUCR
>     www.numis.northwestern.edu/ <http://www.numis.northwestern.edu/>
>     Research is to see what everybody else has seen, and to think what
>     nobody else has thought
>     Albert Szent-Gyorgi
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>
>
>
> -- 
> 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 <mailto:evgeniya at theochem.tuwien.ac.at> 
> http://www.imc.tuwien.ac.at
>
>
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