[Wien] Why is the calculated lattice volume only the half of the unit cell volume of CoSb3?

[Stefaan Cottenier]

>      I use the latest vision of wien2k to optimize the lattice 
> paremeter of CoSb3(space group is Im-3 and the number of space group 
> is 204). And I choose the option of "vary VOLUME with constant a:b:c 
> ratio" at the first step. The lattice parameter of CoSb3 is 
> 17.07955404 a.u. and the vomume of the unit cell is 4982.296631 cube 
> a.u.. There is no error in the process of calculation of optimization. 
> However, the calculated volume of unit cell is only the half of the 
> unit cell  volume of CoSb3.  Is the calculated result right? What is 
> the matter?Please help me. By the way, what is the relation between 
> the conventional cell and the unit cell of CoSb3? Thank you very much.

In body centred symmetry (all space groups starting with I, or in wien2k 
convention with lattice type B in case.struct), the primitive unit cell 
has half the volume of the conventional unit cell. The lattice constants 
in case.struct are for the conventional unit cell. The :VOL label in 
case.scf is for the primitive one.

Stefaan


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