[Wien] ENE Si vacancy

[Stefaan Cottenier]

> * 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).

Do you mean the :NOE label in case.scf2? If you have 25 atoms in your CXY
case.struct (= 25 lines with xyz-coordinates), then :NOE should give the
number of valence electrons for 25 atoms. Be aware that 'valence electrons'
is defined as 'electrons with an atomic eigenvalue larger than the
separation energy given in lstart', which is something different from 'all
electrons outside the noble gas core'. If you doubt, look in case.inc to see
which electrons are core electrons (all the others are valence), or in
case.scfc (or case.scfcup/dn) to see the same information in more legible
form.

Also, if you do a magnetic calculation, don't confuse the meaning of :NOE
and :CHA. The latter is often more or less one half of the number of
electrons, as it is given per spin channel. :NOE is always for both spin
channels (and therefore necessarily integer, while :CHA need not to be).

Stefaan