[Wien] ENE Si vacancy

[Peter Blaha]

> * I would like to have a clarification on the number of atoms per supercell :
> 
> When creating my supercell (Si crystal) 2x2x2 Primitive i have obtained 32
> atom supercell according to the struct file.  This has been reduced to 26
> atoms (25 + vacancy) in the CXY crystal symmetry.
> 
> My question is that when i look in the SCF2 file the number of valence
> electrons corresponds to 64 atoms (63 + vacancy), therefore i have come to the
> conclusion that my supercell (above) represents 64 atoms instead of 32
> (clearly this can be seen SCF2 and also XcrysDen).

If you start with FCC Si (2 atoms in FCC cell) and apply supercell with
P lattice and 2x2x2 this yields a struct file with 64 atoms:

2 Si * 4 (F-->P) *2x2x2 = 64 atoms.
      
I don't understand the comments about 32 or 26 atoms.
You cannot just look at the second line in case.struct (NAT), but must
"count also the MULTiplicity of the different sites).

                                      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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