[Wien] AFM calculation

[thomas.mazet]

Dear Sir,


About your second question concerning the non-zero magnetic moment on Bi 
and O atoms (I have not verify the details of your input files) : it is 
normal that in magnetic compounds (even in antiferromagnets) nominally 
'diamagnetic' atoms possess a low magnetic moment : it is induced by 
spin-dependent chemical bonds with the magnetic atoms (like iron). You can 
think in terms of molecular fields : if the magnetic configuration of the 
neighboring iron moments around Bi or O is such that it leads to a 
non-zero molecular field at Bi or O (to be verified), a small magnetic 
moment is expected on Bi ot O. These small magnetic moments on 
nominally non-magnetic atoms are responsible for the hyperfine fields 
at their nucleus you can measure using several experimental 
techniques like RMN, Mössbauer ... There are 
a lot of papers from the seventies, eighties and nineties describing 
this spin-dependent chemical bond  whose authors are Williams, Kubler, 
Johansson, Brooks, Kanamori, Akai ....
I hope it helps you.

Regards,

Thomas



> Dear Peter Blaha , Stefaan Cottenier¡¯s and wien user:
>      I am doing a AFM calculation. In according to the UG and the Stefaan 
> Cottenier¡¯s suggestion, I construct the AFM case.struct. In my original 
> case.struct, I split the positions of the Fe-atoms according to their spin. 
> In the Fe position with MULT=2 has one atom with spin up and one with spin 
> dn, I make one positions with MULT=1 out of it. Give these two different 
> spin types a different label. Run now init_lapw, and accept all structure 
> changes proposed by nn and sgroup. Moreover, I put the correct up and dn 
> occupations for  Fe in the final case.inst file before proceeding with 
> lstart. Then I begin always to use a regular 
> runsp_lapw. The result is :  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
> 
> The original-case.inst and the flip-case.inst as follow:
> Oringial-case.inst
> Bi
> Xe 7 5
> 4, 3,3.0  N
> 4, 3,3.0  N
> 4,-4,4.0  N
> 4,-4,4.0  N
> 5, 2,2.0  N
> 5, 2,2.0  N
> 5,-3,3.0  N
> 5,-3,3.0  N
> 6,-1,1.0  N
> 6,-1,1.0  N
> 6, 1,1.0  N
> 6, 1,1.0  N
> 6,-2,1.0  N
> 6,-2,0.0  N
> Bi
> Xe 7 5
> 4, 3,3.0  N
> 4, 3,3.0  N
> 4,-4,4.0  N
> 4,-4,4.0  N
> 5, 2,2.0  N
> 5, 2,2.0  N
> 5,-3,3.0  N
> 5,-3,3.0  N
> 6,-1,1.0  N
> 6,-1,1.0  N
> 6, 1,1.0  N
> 6, 1,1.0  N
> 6,-2,1.0  N
> 6,-2,0.0  N
> Fe
> Ar 3 5
> 3, 2,2.0  N
> 3, 2,2.0  N
> 3,-3,2.5  N
> 3,-3,0.0  N
> 4,-1,1.0  N
> 4,-1,0.5  N
> Fe
> Ar 3 5
> 3, 2,2.0  N
> 3, 2,2.0  N
> 3,-3,2.5  N
> 3,-3,0.0  N
> 4,-1,1.0  N
> 4,-1,0.5  N
> O
> He 3 5
> 2,-1,1.0  N
> 2,-1,1.0  N
> 2, 1,1.0  N
> 2, 1,1.0  N
> 2,-2,2.0  N
> 2,-2,0.0  N
> O
> He 3 5
> 2,-1,1.0  N
> 2,-1,1.0  N
> 2, 1,1.0  N
> 2, 1,1.0  N
> 2,-2,2.0  N
> 2,-2,0.0  N
> ****
> ****         END of input (instgen_lapw)
> 
> flip-case.inst
> Bi
> Xe 7 5
> 4, 3,3.0  N
> 4, 3,3.0  N
> 4,-4,4.0  N
> 4,-4,4.0  N
> 5, 2,2.0  N
> 5, 2,2.0  N
> 5,-3,3.0  N
> 5,-3,3.0  N
> 6,-1,1.0  N
> 6,-1,1.0  N
> 6, 1,1.0  N
> 6, 1,1.0  N
> 6,-2,0.5  N    <=== equal occup for up/dn
> 6,-2,0.5  N    <=== equal occup for up/dn
> Bi
> Xe 7 5
> 4, 3,3.0  N
> 4, 3,3.0  N
> 4,-4,4.0  N
> 4,-4,4.0  N
> 5, 2,2.0  N
> 5, 2,2.0  N
> 5,-3,3.0  N
> 5,-3,3.0  N
> 6,-1,1.0  N
> 6,-1,1.0  N
> 6, 1,1.0  N
> 6, 1,1.0  N
> 6,-2,0.5  N      <=== equal occup for up/dn
> 6,-2,0.5  N      <=== equal occup for up/dn
> Fe
> Ar 3 5
> 3, 2,2.0  N
> 3, 2,2.0  N
> 3,-3,2.5  N
> 3,-3,0.0  N
> 4,-1,1.0  N
> 4,-1,0.5  N
> Fe
> Ar 3 5
> 3, 2,2.0  N
> 3, 2,2.0  N
> 3,-3,0.0  N       <=== spin flipped
> 3,-3,2.5  N       <=== spin flipped
> 4,-1,0.5  N       <=== spin flipped
> 4,-1,1.0  N       <=== spin flipped
> 
> O
> He 3 5
> 2,-1,1.0  N
> 2,-1,1.0  N
> 2, 1,1.0  N
> 2, 1,1.0  N
> 2,-2,1.0  N        <=== equal occup for up/dn
> 2,-2,1.0  N        <=== equal occup for up/dn
> O
> He 3 5
> 2,-1,1.0  N
> 2,-1,1.0  N
> 2, 1,1.0  N
> 2, 1,1.0  N
> 2,-2,1.0  N     <=== equal occup for up/dn
> 2,-2,1.0  N     <=== equal occup for up/dn
> ****
> ****         END of input (instgen_lapw)
> I have two question:
> 1 Is it right for my claculational method?
> 2 I do no kmow why the MAGNETIC MOMENT of the Bi abd O atom is non-zero?
>    Any help and suggestion is welcome!
> 
> 
> Yours Meng-Qiu Cai
> 
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-- 
Thomas MAZET
Laboratoire de Chimie du Solide Minéral (UMR 7555)
Université Henri Poincaré-Nancy I
BP 239 54506 Vandoeuvre les Nancy Cedex
FRANCE
Tel.: +33-(0)3-83-68-46-77
Fax : +33-(0)3-83-68-46-11