Yes; it's a case of trying to distinguish between a few boulders and
lots of pebbles; the total volume isn't the issue.
What I'm looking at is something like surface/volume ratio, but with
"surface" being path-dependent and gradual. For a nearest-neighbor
path, only the top monolayer of atoms are on the surface. For a 5
angstrom path, the transition region from "surface" to "core" extends
5 angstroms in.
But that more sophisticated definition of "surface" doesn't change the
fact that the dominant dependence is 1/R, so that should address the
issue.
--Scott Calvin
Sarah Lawrence College
On Oct 25, 2010, at 4:43 AM, Matt Newville wrote:
Hi Scott,
That's a pretty amazing use case.
But I'm not sure I understand the issue exactly right. I would have
thought the volume (r**3) was the important physical parameter, and
that a 1000nm particle would dominate the spectra over 3nm particles.
Or is it that you are trying to distinguish between 1 very large
crystal or 100s of smaller crystals? Perhaps the effect you're
really trying to account for is the surface/volume ratio? If so, I
think using Matthew Marcus's suggestion of using 1/r (with a safety
margin) makes the most sense.
--Matt
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