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High-pressure X-ray diffraction studies of the two actinide compounds, UBi and CmBi are reported. These compounds existed initially in the NaCl-type (B1) crystal structure and each was studied at room temperature using a diamond anvil cell and energy dispersive X-ray diffraction analysis. The U and Cm monobismuthides were studied up to pressures of 42 and 48 GPa, respectively. All materials exhibited first-order crystallographic phase transitions from their NaCl-type (B1) to a CsCl-type (B2) structure, which were accompanied by volume collapses: UBi at 5 GPa (11 % volume change); CmBi at 12 GPa (16 % volume change). With curium monobismuthide a subsequent second-order transition from the CsCl-type structure to a tetragonal phase (indexed in space group P4/mmm) occurred at 19 GPa. The bulk moduli and their pressure derivatives were derived for each material from the experimental pressure-volume relationships for the B1 phases. These values were: for UBi, 91 GPa and -5.4; for CmBi, 53 GPa and 8.1.

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Authors: GENSINI M, JRC Karlsruhe (DE);BENEDICT U, JRC Karlsruhe (DE);HAIRE R G, Oak Ridge National Laboratory, Transuranium Research Laboratory (US);HULLIGER F, ETH Zürich, Laboratorium für Festkörperphysik (CH)
Bibliographic Reference: Article: Physica B, Vol. 190 (1993) pp. 75-83
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