________________________________
Post #5
Crystal- structure
of Nickel, plus some back-of-the-napkin calculations
Ref:
http://www.webelements.com/nickel/crystal_structure_pdb.html
use the
interactive view.
distance between
atoms: 352pm.
(Btw, Pd and quite some others (Cu) has a similar crystal-structure with
slightly larger atomic distance)
So a
nanocrystal-cube of 3.5nm^3 would
comprise 10x10x10 =1000 atoms.
The
percentage of atoms on the surface to those in the volume is in the order of
50%!
Now Ahern
says the following in his ppt- presentation (ref -- see my post#1) page 10:
…All nanoparticles in this size regime will display energy localized
vibrational modes. They will be able to catalyze energy transfers as if they
were very hot, localized energy reservoirs. …
If in a
crystal with nonlinear vibrational modes ALL energy is concentrated in one
atom for a short time,
this would mean that the kinetic energy of this single atom could be not more
than the average energy of the 1000 atoms.
By far not enough
to overcome the coulomb-barrier with a classical approach.
Then there
are the protons (H+ ions) diffusing into the Lattice, and are push-pulled by
the lattice-vibration.
Ahern states
that the temperature has to be elevated
to something like 500K for the reaction to start.
This gives
some starting point for the energetic (kinetic) state of a Nanoparticle
Aspects to
consider: quantum tunneling; Gamov window (Wikipedia)
