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?
Andrea L. Foster, Ph.D.
345 Middlfield Rd., MS 901
Menlo Park, CA 94025
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