[Wien] AFM calculation

[蔡 孟秋]

Dear Stefaan and Thomas:
     Thank you very much for your detailed explanations. I have known that 
the non-zero magnetic for the non-magnetic atoms is induced by the
spin-dependent chemical bonds with the magnetic atoms.

   Now I have the other questions. In according to the UG, the 
AFM-calculation will save us more than a fractor of 2 in computer time, 
since only spin-up is calculated and in addition the scf-convergence may be 
much faster. When I select the AFM-calculation, it asks me if the 1/1 , 1/2 
... atoms have the same spin density?  I do not know what it mean and how 
to select the answer (Y/N). In my calculation, I select No for all. Is it 
right?

  Moreover, the results for normal SP-calculation and AFM-calculation in my 
case are as followed:


Normal SP-calculation 
   MAGNETIC MOMENTS OF MIXED CHARGE DENSITY
:MMINT: MAGNETIC MOMENT IN INTERSTITIAL =    0.00000
:MMI001: MAGNETIC MOMENT IN SPHERE   1    =   -0.00256
:MMI002: MAGNETIC MOMENT IN SPHERE   2    =    0.00255
:MMI003: MAGNETIC MOMENT IN SPHERE   3    =    3.66726
:MMI004: MAGNETIC MOMENT IN SPHERE   4    =   -3.66725
:MMI005: MAGNETIC MOMENT IN SPHERE   5    =    0.05963
:MMI006: MAGNETIC MOMENT IN SPHERE   6    =   -0.05963
:MMTOT: TOTAL MAGNETIC MOMENT IN CELL   =    0.00000

:ENE  : ********** TOTAL ENERGY IN Ry =       -92320.574106
:DIS  :  CHARGE DISTANCE       0.0018354

AFM-calculation:


       MAGNETIC MOMENTS OF MIXED CHARGE DENSITY
:MMINT: MAGNETIC MOMENT IN INTERSTITIAL =   -0.37953
:MMI001: MAGNETIC MOMENT IN SPHERE   1    =    0.04557
:MMI002: MAGNETIC MOMENT IN SPHERE   2    =   -0.04557
:MMI003: MAGNETIC MOMENT IN SPHERE   3    =    3.95686
:MMI004: MAGNETIC MOMENT IN SPHERE   4    =   -3.95686
:MMI005: MAGNETIC MOMENT IN SPHERE   5    =    0.00000
:MMI006: MAGNETIC MOMENT IN SPHERE   6    =    0.00000
:MMTOT: TOTAL MAGNETIC MOMENT IN CELL   =   -0.37953


:ENE  : ********** TOTAL ENERGY IN Ry =       -92290.228557

:DIS  :  CHARGE DISTANCE       0.0001840

Now I have two questions:

1 I do not know why the total magnetic moment in the cell for the 
AFM-calculation is non-zero?
2 I do not know why there are two different results for the normal 
SP-calculation and AFM-calculation for the same parameter?  Why or not for 
the improper AFM-input?

Any help and suggestion is welcome!


Regards,

Meng-Qiu Cai





>From: "Stefaan Cottenier" <Stefaan.Cottenier at fys.kuleuven.ac.be>
>Reply-To: wien at zeus.theochem.tuwien.ac.at
>To: <wien at zeus.theochem.tuwien.ac.at>
>Subject: Re: [Wien] AFM calculation
>Date: Fri, 14 Jan 2005 14:11:08 +0100
>
> > 1 Is it right for my claculational method?
>
>Yes, this seems to be perfectly OK. Out of the 3 elements in your 
structure
>(Bi, Fe, O) only Fe is expected to carry a sizeable moment, which is 
indeed
>what you found:
>
> > :MMINT: MAGNETIC MOMENT IN INTERSTITIAL =    0.00000
> > :MMI001: MAGNETIC MOMENT IN SPHERE   1    =   -0.00256(Bi)
> > :MMI002: MAGNETIC MOMENT IN SPHERE   2    =    0.00255(Bi)
> > :MMI003: MAGNETIC MOMENT IN SPHERE   3    =    3.66726(Fe)
> > :MMI004: MAGNETIC MOMENT IN SPHERE   4    =   -3.66725 (Fe)
> > :MMI005: MAGNETIC MOMENT IN SPHERE   5    =    0.05963 (O)
> > :MMI006: MAGNETIC MOMENT IN SPHERE   6    =   -0.05963 (O)
> > :MMTOT: TOTAL MAGNETIC MOMENT IN CELL   =    0.00000
>
>Your two Fe-atoms are antiferromagnetic, just as you wanted them to be.
>
> > 2 I do no kmow why the MAGNETIC MOMENT of the Bi abd O atom is 
non-zero?
>
>In a compound between 'magnetic' and 'nonmagnetic' elements, never the
>moments on the nonmagnetic atoms will be perfectly zero. The magnetic 
atoms
>induce some magnetism on the nonmagnetic ones. For an antiferromagnetic as
>you have, these induced moments themselves are antiferromagnetic (one Bi 
has
>a positive moment, the other a negative one, similarly for O). They are 
two
>(O) or three (Bi) orders of magnitude smaller than the Fe moments, in a
>qualitative description this is considered as 'zero'.
>
>Stefaan
>
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>Wien at zeus.theochem.tuwien.ac.at
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