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Re: Induced dipole moments



At the end of his reply John Mallinckrodt wrote:

... But, leaving alone the previous error, you haven't provided
a demonstration that your assumed structure would be stable in
any event. I could easily imagine, for instance, that the most
stable configuration, at least for some range of strengths for E,
would involve a displacement along a body diagonal of the cube.

Good point. Here is a trivial illustration (when E=0). Suppose
that the "rigid cloud" consists of only two electrons, one on
the left and one on the right. This configuration is stable along
x direction but unstable along the y direction. A ring of
electrons would provide stability in the x,y plane but this
system would still be unstable along the z axis.

A spherical shell of charge? Hmm, not really! Here the
restoring force is zero everwhere. The neutral equilibrium is
not the same thing as real equilibrium in the center of a
uniformly charged sphere. I suppose that this is not the only
way to trap +Q in the center of a structure made from pieces
of -Q. What about an oxygen nucleus in the center of a cube
made of 8 electrons, one at each corner?

The world is made of netral atoms; most atoms are stable.
Everything must be in motion to produce stability (which
rimes with immobility). Right? What a world !
Regards, Ludwik