XANES study of K edges of Fe, Co, Ni, and Se in transition metal selenides. Experiment and comparison with LMTO numerical calculations

In our study we investigate the transition metal (TM) K-edges as well as Se K ones and compare them with LMTO (linear muffin tin orbital) calculations . We discuss the structure of the edge on the basis of trigonal (not octahe dral) coordination of the cation. In the numerical section we show that a q uantitatively small difference between experimental anion edges of TM sulph ides and selenides is larger in the theoretical DOS which shows larger loca lisation of electrons (narrower bands). In the experiment this effect is ma sked by the finite width of an initial state. Also it has been shown that t he common pre-peak in cation K edges can be explained on the basis of one e lectron numerical calculations and thus places this feature above the edge (not under E-0) and does not require symmetry breaking in dipole transition approximation (transition from 1s to d-like DOS). (C) 1999 Elsevier Scienc e S.A. All rights reserved.