; Zhong, Jun
; Wu, Xiang
; Wu, Ziyu] Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China
; [Mironova-Ulmane, Nina
; Kuzmin, Alexei] Latvian State Univ, Inst Solid State Phys, LV-1063 Riga, Latvia
; [Marcelli, Augosto] Ist Nazl Fis Nucl, Lab Nazl Frascati, I-00044 Frascati, Italy
A series of NicMg1-cO solid solutions are characterized by means of synchrotron radiation X-ray diffraction and X-ray absorption near-edge-structure spectroscopy at oxygen K-edge (532 eV). A dramatic drop of the pre-edge peak intensity is observed in the NicMg1-cO system upon dilution. It can be attributed to a decrease of 3d(8)(Ni2+)-2p(O2-) mixing upon dilution with magnesium ions due to a decrease of the number of 3d vacancies as nickel ion is replaced by magnesium ion. Similarly, the decrease of the number of 4s and 4p vacancies also leads to a decrease of 4s4p(Ni2+)-2p(O2-) hybridization, and hence a drop of intensities of features B and C. The features E and F are more sensitive to the increase of the degree of disorder upon dilution than feature D, revealing that the latter is mainly dependent by the medium-range order. (C) 2008 Elsevier B.V. All rights reserved.