[Pw_forum] How to obtain the binding energy ( in the unit of eV/Zn-O pair ) for Wurtsite ZnO?

[Hongsheng Zhao]

On 05/28/2011 02:44 AM, mohnish pandey wrote:
> Dear Hongsheng,
>  All the four bonds in ZnO wurtzite are equivalent.
But the four bonds have different bond lengths: the bond length parallel 
to c axis is different from that of the other two bonds.  Why can you 
say are equivalent?

> So to calculate the binding energy you have to use the below formula :
> E_{binding-ZnO}=E{calculated-ZnO-wurtzite}-E_{Zn_{crystal-total}}-E_{E(1/2*O2}}.
>  Remember that you have to do spin-polarised calculation for O2 
> otherwise it will give wrong answer.
I've learned that this is due to O atom's open-shell configuration. Than 
what is the initial spin should I use for O2?

Furthermore, for ZnO wurtzite, should I do spin-polarised calculation or 
not?

> Binding energy definition is same as above. And cohesive energy is the 
> difference in energy between the energy of crystal and corresponding 
> species in isolated phases. Below are the some references.
Do you mean, for the calculation of cohesive energy, I should use the 
big box model, then put one Zn in the big box, and O atom in another box 
to obtain the total energy of each isolated phases?

> http://arxiv.org/ftp/cond-mat/papers/0610/0610002.pdf
> http://prb.aps.org/pdf/PRB/v70/i5/e054104

Regards.
-- 

Hongsheng Zhao<zhaohscas at yahoo.com.cn>
School of Physics and Electrical Information Science,
Ningxia University, Yinchuan 750021, China