Subject: Re: CCL:ET at short distances

From: Harald Svedung <[email-masked]>
Date: Tue, 13 Aug 2002 11:19:55 +0200 (CES)

Hello Arturas and all.

How is life on Gediminas Avenue?

At 3 AA, a first order SCF calculation should do the job. That is to say
an intermolecular interaction is then dominated by exchange repulsion.
This corresponds to a Born-Meyer repulsion in the Electron Gas Density
Functional method:

C. Nyeland, J. P. Toennies, Chem. Phys., 188, (1994), 205.

We tested this in:

H. Svedung, S. Nordholm, C. Nyeland, PCCP, 3, (2001), 2209.

V(Born-Meyer) = A exp(-b*r),

and we found, e.g., that b for an He-He interaction is 2.35 and for an
Ar-Ar interaction 1.93.

The density and shape of the HOMO clearly comes into play, but unless the
LUMO is very close, or if you consider extremly strong collisions, the
LUMO will probably not mix into the solution. That is if we are talking about
the interaction between two molecules.

The environment of the interacting centra will change the results as the
electron density is changed, but the effects are not huge.... depending on
how sencitive you are.

:-)
/Harald

On Mon, 12 Aug 2002, Arturas wrote:

> Hello CCL'ers,
>
> Got qustion, if anybody back at work again :)
>
> It is postulated that in long range ET there is exponential dependence
> and the main factor controling ET is distance. Here is distances above
> 5 Angstroms. If we have two molecules at distance shorter than 5; say
> about 3-4 Å.
>
> How large can be ET deviation depending on structural arrengments for
> each other (Acceptor-Donor) ??? Can some orientation retard ET so that
> ET rate would drop significantly ??? Do any structural things play any
> influence in short distance or, in opposite, in short distances all
> depends on HOMO/LUMO properties saying roughly ???
>
> Would like to get just any short profesinal comments.
>
> --
> Best regards,
> Arturas Z.
>
> mailto:[email-masked]
> http://biologija.vdu.lt/person/ziemar/index.html
>
>
>
>
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Dr. Harald Svedung                       cellphone: +49-175 736 2576
Institut für Physikalische Chemie               or: +46-709-223 206
Universität Karlsruhe
Fritz-Haber-Weg 4
D-761 28  Karlsruhe
Tyskland
Tel: +49-721 608 2108
Fax:+49-721 608 6524