Subject: How to define HOMO-LUMO gap in open shell system ?

From: "Ding Xunlei" <dxl=at=ustc.edu.cn>
Date: Tue, 28 Jun 2005 08:34:00 +0800

Dear Sir/Madam#:

A open shell system has the MOs like this:

#- #-4  #- #-5    
        #- #-3  
#-x#-2  
#-x#-   #-x#-1  
#-x#-   #-x#-   
#-x#-   #-x#-   
alpha    beta 

MO with "x" has an electron occupation.
Then how to define the HOMO-LUMO gap of this system? 
To define on gap as
E_gap=E3-E2
or to define two gaps for alpha and beta as
E_gap=E3-E1, and E_gap=E4-E2 ,respectively?

Yours sincerely, 				
Ding Xunlei
2005-06-28
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