Re: [SI-LIST] : Atomic animation

Douglas McKean (dmckean@corp.auspex.com)
Wed, 17 Feb 1999 10:35:06 -0800

Doug,

Current flow of electrons can be described with a couple
of concepts. One has to do with "mean free path".
There's an average distance that the electron will
travel within a Cu lattice before it impacts a Cu atom.
And several things can happen after impact, if can deflect
off the atom, get absorbed with no re-emission, or get
absorbed with a re-emission of an electron.

Another is "mobility" which has to do with the ratio
of "drift velocity" to "applied electric field".
That can be analogous to gas diffusing from point A
to point B with some help from the applied field.

Introducing this concept for the first time, I'd recommend
the mean free path model (I think I know where you're doing
your presentation). I don't remember the exact mean free
path for an electron in Cu but it's something like
400 angstroms (don't bet on this number). In contrast,
super conductors can have mean free paths above a kilometer.
That's why super conductors are so good at conducting.

I'm sure someone here would have exact numbers,
but if not, I'll try to dig them up.

Regards, Doug McKean

At 04:46 PM 2/16/99 -0800, Doug Brooks wrote:
>I am working on a presentation where I will be talking about the following:
>1. current is the flow of electrons.
>2. Some atoms are better conductors of current than others because of the
>number of free electrons in their outer shell (for example, copper, gold,
>and silver all have just one electron in their outer shell.)
>
>I am looking for a model or an animation of atomic structure that will help
>make this point. At this point I am even willing to settle for a good
>picture!!
>
>Can anyone help point me to a resource where I can find something that will
>help?
>
>Thanks
>Doug Brooks
>
>
>

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