Subject: resonance integrals in HyperChem's ZINDO

From: "Ronald L. Musselman" <[email-masked]>
Date: Wed, 30 Oct 2002 13:43:52 -0500

Hello ZINDO users:

	I'm having some trouble ferreting out the details regarding 
beta values (resonance integrals), etc. in ZINDO, especially the 
implementation from HypeCube, with regard to UV-vis spectral 
calculations.  The manual (CC, p307) leaves a lot unstated.  I'd 
greatly appreciate being directed to a good source that deals with 
these specifics, or even a short direct answer if possible.

My understanding of the relationship among resonance and overlap 
integrals is that,

	beta_uv = beta_AB * S_uv

where u refers to MO_u  on atom A, v refers to MO_v on an adjacent 
atom B, beta_uv is the resonance integral, beta_AB is the overlap 
weighting factor, and S_uv is the overlap integral.  Is this correct?

	Assuming the above is OK, I understand that the overlap 
weighting factors in HyperChem7 are intended to provide better 
results when doing spectroscopic calculations.  Thus, the factors 
should be 1.0 when using ZINDO/1 and not 1.0 when using ZINDO/S.  My 
question, then is, if the weighting factor adjusts the S_uv for a 
better beta_uv for spectra, why does it appear that there are 
different values of beta_uv for ZINDO/1 and ZINDO/S?  Is this not 
double adjusting?

	Perhaps a more fundamental question is, are the beta s,p, and 
d values listed in files zindo1_1.abd and zindoS_1.abd the same as 
beta_uv in the equation above?

	Also, there appear to not be any weighting factors for d 
orbitals; is this true?

	Thanks to those who have read all the way down to here!

		Sincerely,

			Ron Musselman
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