Hello All, can someone please help
with this:
(1) feff requires that the adsorbing
atom be "embedded" (that is, surrounded by) other atoms
in order to calculate potentials correctly, but how deeply does the atom
need to be embedded?
For example, if I construct a
model of an adsorbate on a mineral surface, where that adsorbate has a
full complement of 1st shell coordinating OH, O, and H2O groups as appropriate,
but if I do not include all the uncoordinated f water atoms that would
be nearby (so that I essentially have a surface in vacuum), will the potentials
for my central atom be calculated correctly (or correctly enough for use
in IFEFFIT)?
a more specific example: the AsO4 tetrahedron
bonded to the goethite surface, which is made of octahedrally-coordinated
iron. The arsenate bonds to the goethite by sharing 1 edge
of the tetrahedron with the apices of 2 adjacent Fe octahedra.
a related question that comes to mind:
if I just wanted to see the signal from the 2 adjacent Fe atoms, could
I create a perfectly "useable" FEFF model (for IFEFFIT) by limiting
my calculations to the small cluster of 1 arsenate tetrahedron and 2 Fe
octahedra?
thanks, andrea
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Andrea L. Foster, Ph.D.
U.S.G.S. WMESC
345 Middlfield Rd., MS 901
Menlo Park, CA 94025
T: 650-329-5437
F: 650-329-5491