[Pw_forum] Local magnetic moment

[Gabriele Sclauzero]

On 08/22/2010 08:16 PM, Duy Le wrote:
> If an electron has negative Sz, its magnetic moment would be negative. 
> Sz of majority spin electrons in your system is negative.

More pragmatically, I would say that the number of spin-down electrons 
(projected onto the atomic orbitals of that atom) is larger than the 
number of spin-up electrons. That's how the magnetization is calculated

m=(\rho_{up} - \rho_{down})/\rho_{tot}

where

\rho_{tot} = \rho_{up} + \rho_{down}

> Just flip the molecule (system) 180o (change direction of z 
> coordinate) you will get positive magnetic moments

I don't think this will work. The spin space is other than the atomic 
coordinate space and, unless there is a spin-orbit coupling interaction, 
they are decoupled at the LSDA level. In order to reverse the 
magnetization you could try to start with opposite 
starting_magnetization(i) w.r.t. to your present starting value(s).

> (but you don't have to).

I agree, you will get the same total energy.


HTH

GS


> --------------------------------------------------
> Duy Le
> PhD Student
> Department of Physics
> University of Central Florida.
>
> "Men don't need hand to do things"
>
>
> On Sun, Aug 22, 2010 at 2:02 PM, Padmaja Patnaik 
> <padmaja_patnaik at yahoo.co.uk <mailto:padmaja_patnaik at yahoo.co.uk>> wrote:
>
>     Dear all
>     I have a doubt in the value obtained for local magnetic moment of
>     the atoms. The pdos.out file, towards its end shows the value of
>     polarization on each atom of the sample which gives us the value
>     of local magnetic moment of each atom. Many of these values are
>     found to be negative in my calculations. What does it mean? How
>     can a magnetic moment value be negative?
>
>
>     Regards
>     Padmaja Patnaik
>     Research Scholar
>     Dept of Physics
>     IIT Bombay
>     Mumbai, India
>
>
>
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-- 

Gabriele Sclauzero, EPFL SB ITP CSEA
PH H2 462, Station 3, CH-1015 Lausanne

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