[Wien] Question on symmetry

[Peter Blaha]

It is a well known fact that SO may reduce the symmetry (and this can be 
different for different directions of magnetization).

And yes, this symmetry reduction can even lead to a "splitting" of 
equivalent atoms and make some atoms non-equivalent.

symmetso does not give you explicitely the spacegroup number, but dedects 
the correct symmetry operations, which is all you need for an scf 
calculation.

>    I am trying to study SmCo4B which crystallizes in
> the CeCoB type. It has 
>    two Sm atoms at (0,0,0) and (0,0,1/2) : eight Co
> atoms at 
>   (1/3,2/3,0) ,(1/2,0,0.287) and two B atoms at
> (1/3,2/3,1/2) lattice 
>    parameters a=9.46 A and c= 12.97 A space group
> 191P6/mmm.
> 	
> 	I would like  to calculate anisotropy energy so I
> have to do spin orbit 	calculation with magnetization
> along (001) and (100) directions
> 
> My questions are
> 
> 1- Why the number of inequivalent atoms when
> magnetization in 
>    001 direction is different than 100 direction.
> 
> 2- The spin-orbit reduces the number of symmetry
> operations 
>    from 24 to 8.when one go from 001 to 100 direction.
>    In that case do I have new space group? If so Can
> wien2k 
>    detect the new possible change in structure and the
> new space group.
> 	   
> 
> 	Thanks all for your kind help and advice
> 	
> 	with my best regards  and happy new year 
> 	    
> 	 
> 
> 
> 	
> 		
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                                      P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
Email: blaha at theochem.tuwien.ac.at    WWW: http://info.tuwien.ac.at/theochem/
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