[Wien] About the occupation number

[Hua Wu]

On Tuesday 30 August 2005 16:42, zhoukj wrote:
>
> I read the example in Wien that TiO2.scf:
> ......
>
> :CHA001: TOTAL CHARGE INSIDE SPHERE   1 =     9.410515
> :PCS001: PARTIAL CHARGES SPHERE =  1 S,P,D,F
> :QTL001: 2.0814 5.9725 1.2991 0.0464
>
> ....
> ...
>
> :CHA002: TOTAL CHARGE INSIDE SPHERE   2 =     5.216109
> :PCS002: PARTIAL CHARGES SPHERE =  2 S,P,D,F
> :QTL002: 1.5925 3.6100 0.0103 0.0026
>
> ...
> ...
>
> :CHA  : TOTAL CHARGE INSIDE UNIT CELL =      48.000000
>
> ...
> ...
>  CHARGES OF MIXED CHARGE DENSITY
>
> :CTO  : TOTAL   INTERSTITIAL CHARGE=  8.3145331
> :CTO001: TOTAL   CHARGE IN SPHERE  1 = 19.4105152
> :CTO002: TOTAL   CHARGE IN SPHERE  2 =  7.2161092
>
> ....
> ....
> So, we can find that Ti 3d electrons belong to MT sphere are
> 1.2991.  But due to insulator of TiO2, I think Ti4+ should
> have very little 3d charges.I don't know what's the reason.
> According to my opinion, QTL*** couldn't tell us true
> occupation of shells of different materials.
>
The QTL** number is muffin-tin size dependent, and it is
meaningful (when comparsion is made for various oxidization
states, e.g. TMO, TM_2O3 et al) but not exactly physical.

For TiO2, formally the Ti is 4+ and has 3d^0. However,
in TiO2  the 'Ti4+' ions are not isolated ones, and they 
have chemical bondings (besides the Ti4+/O2- attraction)
with oxygens and probably with neighboring
Ti images to form solid. It is the Ti-O bondings which
bring some charge back to Ti3d.  

regards -- H. Wu