OK, I checked my bond lengths against webelements.com. In all cases
my bond length data matched theirs to their precision, except for a
minor difference with Pt, which I fixed in Table 1 of the following:
<http://www.mtaonline.net/~hheffner/CCP.pdf>. This difference is not
significant.
However, I noticed in the crystallography page they referred to a CPP
structure, not FCC for Pd. In this structure the atomic "balls" all
push right up against each other. In other words, their atomic radii
are equal to the bond length divided by 2. I computed Table 1 on
this basis. As you can see, both the tetrahedral space and face hole
tend to be even more cramped than by the FCC assumtions. This was
especially true for Pb.
Using the webelements van der Walls radius of 1.2 angstroms, there is
no way atomic hydrogen fits *anywhere* in any CPP element. Using the
covalent radius of 37 a single atom of an H2 molecule still fits a
tetrahedral space, but a full H2 molecule doesn't quite fit. This
still permits the "anvil" effect portrayed in the original AEH
paper. If we use the emperical atomic radius of 25 pm, however,
atomic hydrogen fits easily into any tetrahedral space, but still can
only diffuse through Sr, Pb, Ca, Yb, and Ce without tunneling.
I don't see these refinements, if they be such, as significant to the
overall theory.
Horace Heffner
On Jan 11, 2006, at 5:34 AM, [EMAIL PROTECTED] wrote:
Here's the reference on Pd radius:
http://www.lenntech.com/Periodic-chart-elements/Pd-en.htm
although I now see that wikipedia has different numbers:
http://en.wikipedia.org/wiki/Palladium
Here's the xtal dimensions:
http://www.webelements.com/webelements/elements/text/Pd/xtal.html
And here's the reference from NRL on the lattice expansion:
http://www.mse.ncsu.edu/CompMatSci/papers/MH1_science.pdf
