Subject: SOMO of the radical

From: "Adrian Radomir Jaszewski" <[email-masked]>
Date: Mon, 10 Apr 2000 15:30:16 MET

Dear CCLers,

>From N linearly independent basis functions of the radical (S=1/2)
one can construct N alpha and N beta orbitals:
N alfa = (n-1) CORE + 1 SOMO occupied + (N-n) VIRTUAL
N beta = (n-1) CORE + 1 SOMO unoccupied + (N-n) VIRTUAL
where n denotes the number of electrons. 

Unrestricted DFT wavefunctions of the radicals are usually 
constructed using identical (or almost identical) spatial orbitals 
for different spins (alpha, beta) in the case of CORE and VIRTUAL
MO.
Lowest energy (occupied) alpha-spin SOMO and highest energy 
(unoccupied) beta-spin SOMO can be also very similar to each other 
but sometimes they are strongly asymmetrical. A knowledge of 
the SOMO contour can be helpful in the analysis of the spin density 
distribution as well as the values of the calculated hyperfine coupling 
constants for the radicals.

My question is:
When SOMO occupied (alpha) and SOMO unoccupied (beta) are 
dissimilar which of them (or what combination of these SOMOs) 
can be used to aid spin density analysis?
In some cases I have observed that the spin density contours were 
similar to the highest energy beta-spin SOMO (unoccupied!!) contour
 rather than to the occupied alpha-spin SOMO; and what is the 
energy (in Hartree) of that SOMO when:      
E(lowest energy VMO)= -0.06916(alpha) -0.06008(beta)
E(highest energy SOMO)= -0.12635(beta)  
E(lowest energy SOMO)= -0.26301(alpha)
E(highest energy DOMO)= -0.24908(alpha) -0.24319(beta)?

I will summarize.
Thank you in advance.

Adrian

===============================================
Adrian R. Jaszewski
Faculty of Chemistry
UNIVERSITY OF WROCLAW
14 Joliot-Curie St.
50-383 Wroclaw
Poland
e-mail: [email-masked]
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