Determination of the Factorized Atomic Part
of the X-ray Absorption Cross Section in the Near-Edge
Spectrum: Application to the Analysis of Structural Changes
frame0 Zeolite with an Increase in the Aluminum Content

L. A. Bugaev, Ya. V. Latokha, L. A. Avakyan, and E. Ya. Fain

Rostov State University, Rostov-on-Don, 344090 Russia


Received September 13, 2006

Abstract—A technique for determining the factorized atomic part at(k) of the X-ray absorption cross section
in the near-edge range of small photoelectron wave numbers k, based on the selection of this function from the
experimental absorption spectrum of the atom in a compound, has been developed. This technique has been
tested using the X-ray absorption near-edge structure (XANES) spectra of aluminum and silicon in a number
of model compounds with known structure and applied to investigation of changes in the character of the short-
range environment of a silicon atom in zeolite with a variable Si/Al ratio. Use of the function at(k) obtained
by the developed technique in the ab initio calculation of the XANES spectra of silicon in a model zeolite
with Si/Al = 100 makes it possible to reduce the effect of the errors of the muffin-tin approximation on the fine
structure of the calculated spectrum and substantiate the possibility of comparing relative changes in a certain
spectral range with a change in the structure of the short-range environment of silicon in zeolite with an
increase in the aluminum content. On the basis of this approach, the formation of local distortions in the oxygen
tetrahedron coordinating an ionized silicon atom with an increase in the aluminum content (decrease in the
Si/Al ratio from 100 to 12) has been established.

PACS numbers: 78.20.Ci

DOI: 10.1134/S0030400X07060100

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