[Pw_forum] one strange result about the phenazine molecule

[Giuseppe Mattioli]

Dear Dai Zhenxiang
You may be aware that DFT eigenvalues depend on the  
exchange-correlation functional employed in the calculation. Chemists  
usually use B3LYP for database purpose (it is not indicated in the  
link you provided, so I assume that it is B3LYP). Which xc functional  
have you used in your calculation?
You might enjoy this paper if you are puzzled by my considerations...

Cohen, A. J.; Mori-Sànchez, P.; Yang, W. Insights into Current  
Limitations of Density Functional Theory. Science 2008, 321, 792−794.

HTH
Giuseppe

Quoting Dai Zhenxiang <physdai at qq.com>:

> Dear all:
>   These days I have performed one test calculation about the  
> phenazine molecule.
> From the  website Nanoniele, it can be found that its HOMO-LUMO gap  
> should be 3.654eV.
> http://www.nanoniele.jp/cgi-bin/nanoniele.cgi?inputsite=ranking_HOMO_China%20Telecom&rankingflag=homolumo&inputid=174679811422510&keyword=phz
> However,  my QE calculation suggests HOMO-LUMO gap is only about  
> 2.20 eV. So, the difference is very, very big !
>
> These corresponding files are attached. Would you like to give me  
> some advice?
>
> Best wishes!
>
> DAI


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    Giuseppe Mattioli
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