[Pw_forum] Co Pseudopotential

[giuseppe.mattioli at mlib.ism.cnr.it]

Really not surprising...
I've performed some calculations on Co-phthalocyanine, that is, a  
Co(II) ion "dressed" by an organic molecule (odd number of electrons,  
S=1/2 on cobalt), in contact with a Pb surface (even number of  
electrons). A charge transfer of one electron from the Co atom to the  
Pb slab quenches the Co magnetic moment to S=0, as also measured by  
spin-polarized STM.
As Heather and Jia say, it may be very important to know if some  
charge transfer process between your "undressed" (:-)) Co atom and  
your (metal?) slab takes place. It should depend on the relative  
positions of the Co electronic levels with respect to the metal Fermi  
energy (enough k points...?). You may check this also by using the  
pp.x code in order to subtract the Co and slab charge density to the  
total (Co+slab) charge density, thus obtaining an .xsf charge density  
plot you can look at with xcrysden.
Beyond GGA methods (GGA+U on the 3d shell of Co?) may be also useful,  
if you are able to calculate/estimate a meaningful value for the  
Hubbard U.
HTH. Without looking at your real system it is unlikely we can advice  
you more than this, I suppose...

Giuseppe


Giuseppe Mattioli
ISM-CNR
Italy

Quoting jia chen <jiachen at princeton.edu>:

> Hi,
>
> If I understand you correctly, there is electron transfer between the
> surface and the Co atom which makes the spin polarization of Co atom to be
> 1. Not very surprising to me.
>
> On Mon, Aug 8, 2011 at 7:16 PM, Izaak Williamson <izaakw89 at yahoo.com> wrote:
>
>> Thank you Heather and Jia for your replies. For a single Co atom, I do get
>> the total magnetization of 3 but when Co is on a surface, its spin
>> polarization comes out to be 2, which is S=1. The all-electron calculations
>> were also done using pbe functional and on the same surface and with the
>> same coverage of Co.
>>
>> Heather, what do you mean by locally? I do calculate the spin polarization
>> from pdos. The whole system does have an even number of electrons but why
>> does it result in S=1? Any explanation would be appreciated.
>>
>>
>> --
>> Izaak Williamson
>> Research Assistant
>> Physics Department
>> Boise State University
>>
>>
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>>
>
>
> --
> Jia Chen
>