U ternaries with ZrNiAl structure - lattice properties

The bonding properties of UTX compounds having the hexagonal ZrNiAl-type st ructure display a pronounced anisotropy. The compressibility and thermal ex pansion reach values several times higher for the basal plane than along th e c-axis. This situation also occurs for the Th-containing counterparts, wh ereas it is absent in isostructural materials based on rare earths. This ph enomenon can be attributed to the participation of the delocalized 5f state s in the bonding, leading to compression of the 5f charge towards the basal plane. This scenario has been investigated theoretically by ab-initio band structure calculations performed for URhAl. (C) 2001 Elsevier Science B.V. All rights reserved.