J. Phys. IV France 7 (1997) C2-219-C2-220
Interpretation of Pre-Edge Fine Structures (PEFS) of K Edge of Vanadium in VOPO4, 2H2OY. Aïfa1, B. Poumellec1, R. Cortès2, R.V. Vedrinskii3 and V.L. Kraizman4
1 URA 446, Lab. CNS, UPS Orsay, 91405 Orsay cedex, France
2 UPR 15, LPLE, ESPCl 75231 Paris, France
3 Dept. of Physics, Rostov State University,. Zorge Str., Rostov on Don 344104 Russia
4 Dept. of Physics, Rostov State University, 5 Zorge Str., Rostov on Don 344104, Russia
A method based on the local density approximation and on the multiple scattering wave calculation taking into account screened X-ray core hole potential for the final state has been used to analyze the experimental XANES spectra of the VOPO4.2H2O xerogel. The effect of cluster size on the computations has been analyzed concluding that the pre-edge depends only on the first shell formed by the six nearest oxygen atoms. In VOPO4.2H2O structure, the absorbing VO6 octahedron is surrounded by PO4 tetrahedra. Thus VO6 octahedra are not linked with each other excluding solid state effect in the pre-edge region. In contrast, edge region is sensitive to the cluster size. Computations show that at least a cluster of V5P4O26 must be taken into account to reproduce, in rather good agreement, the edge part of the absorption spectrum.
© EDP Sciences 1997