Subject: HF and EC bond lengths

From: "Eugene G. Noda" <[email-masked]>
Date: Tue, 25 Nov 1997 17:50:09 +0200

At 04:48 PM 11/24/97 -0500, Jason Lye wrote:
>
> Please correct me if I am wrong; do you mean to say that metal-ligand
> bonding in first row transition metals is predominantly due to 3s and 3p
> orbitals, and that d-orbitals play only a minor role?
>

Dear Jason

No, I can only insist on that 4s and 4p orbitals are redundant elements in
theoretical treatment. As to the role of 3l electrons in the bonding, it
should be proved by direct experiment which is not trivial to my knowledge.

Fig.5.     Besides d-orbitals, I would like to call your attention to
overlapped ligand orbitals. They are calculated using ordinary Slater
basis functions from the literature. You can see that amplitude of
overlapping functions is not much different. Therefore, to neglect
3sp overlap integrals we can only in the case when 3sp orbitals of
d-ion are extremely compact (or frosen to free atomic value).
However, calcs show that situation is different. The average radius
of 3s-3p orbs in matter is near the same as 3d one and these are
stable numerical HF orbitals. As to 4s contribution, I am trying
to catch it many years and, alas, unsuccessfully. This shell is
so high in energy that even ions in matter have lost it :-)
Or, seriously, it seems that 4s task is not simplier than negative
ion problem in atomic calculations (at least in our approach). 

Bonding.     Our modeling shows that at the _typical_ bonding distances
the reordering of crystal subshells (splitted d orbital) leads to their
crossing and thus to formation of new subshells with undetermined symmetry
properties. To restore symmetry, the ligand orbitals should be involved
and the manner of their combination determines the final coordination of
the complex (naturaly, neglecting ligand-ligand interaction). So I believe
that true theory of d-compounds should be a symmetry theory. However,
contrary to usual point group analysis, this theory must be based on the
fact that electronic symmetry of d-ion in matter is dynamical property and
should be determined in self-consistent calculation.

Hope these speculations will be stimulating, Eugene