Structural properties of two deuterides LaY2Ni9D12.8 and CeY2Ni9D7.7 determined by neutron powder diffraction and X-ray absorption spectroscopy

The crystal structure of two deuterides Ry(2)Ni(9)D(x) (R = La; x = 12.8 and R = Ce; x = 7.7) have been investigated by means of neutron powder diffraction and X-ray absorption spectroscopy. The structures are best described in the space group R (3) over barm. The deuterium location has been determined for both compounds. The nature and the occupancy factors of the different D sites are presented. Comparisons are made between the La-based deuteride and the Ce-one in relation with the crystal structure of the intermetallic compounds. Differences in site occupancies within the RM2 and RM5 building units of the PuNi3-type structure are discussed and heterogeneous mixed valence state is reported for the cerium compound. (C) 2004 Elsevier Inc. All rights reserved.