Subject: Re: CCL:G:How to calculate Bond Order ?

From: [email-masked] (Joel Polowin)
Date: Thu, 12 Dec 96 11:37:26 -0500

> From: [email-masked] (Somsak Tonmunphean)
> Date: Thu, 12 Dec 1996 18:55:41 +0000 (WET)
> 
> 	I am doing my thesis with the subject of QSAR of antimalarial 
> drugs. My available chemical calculation softwares are Gaussian 92, 
> Hyperchem release 3, ChemPlus, Alchemy, and Molgen. From some papers, 
> they calculated bond orders and found that these had good correlations 
> with activity so I would like to try it but unfortunately I really don't 
> know how to calculate the bond order of molecules. Does anybody know how 
> to do so (if possible with the programs I have) ? 

It is not possible to calculate bond orders automatically with HyperChem, 
but they can be calculated manually from the density matrices, which can 
be printed in a log file.  The bond order between atoms A and B is the sum 
of the squares of the elements in the density matrix with rows for atom A's 
orbitals and columns for atom B's orbitals, or vice versa.  If you are 
doing UHF calculations, you must add the elements of the alpha and beta 
matrices together before squaring.  I tried this for C2H4 as model-built, 
with an AM1 single-point calculation, and got a C--C bond order of 2.0004.

Joel

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