[Pw_forum] magnetization and lowdin charges

[Axel Kohlmeyer]

On Tue, 24 Apr 2007, Hande Ustunel wrote:

HU> Dear pwscf users,

dear hande,

HU> I have a question concerning Lowdin analysis and the total magnetic
HU> moment. I read on the archives of the forum that one can obtain the
HU> polarization on each individiual atom by running projwfc.x and the
HU> reported polarization should be the magnetic moment on each atom. I

please note, that due the difference in nature of a plane wave
basis set (which covers all space) and a local atomic
basis set (you project on the pseudowavefunctions stored in the
pseudopotentials), there will always be some part of the wavefunction
unassigned, particularly if your wavefunction is very delocalized.

HU> was wondering how, in this case, the units work. Reading the forum I
HU> got the impression that polarization should directly give the
HU> magnetization (in Bohr magneton) without any unit conversion. (
HU> Reading the code, it looks like the differences between up and down
HU> densities is multiplied by something like a volume (I think) to get
HU> the magnetization. ) If that is the case, then if I add up all the
HU> polarizations in the output of the Lowdin analysis, I should more or
HU> less get the "total magnetization" reported by the spin-polarized
HU> output of pw.x. Same argument should also apply to "absolute
HU> magnetization". It turns out for me that the sum does add up to the
HU> total and abs magnetizations in one of my calculations and it doesn't
HU> in two others. It's either the one that works that is just a fluke or
HU> there is a unit conversion issue that I couldn't see from the code or

no. the diference should be somewhat small, but is almost always
noticable and it depends a lot on the type of system you are looking at.

cheers,
   axel.

HU> the archives. I hope I've made it clear enough. Thank you very much in
HU> advance for any help.
HU> 
HU> Best regards,
HU> Hande
HU> 
HU> 

-- 
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Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
   Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
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