NEPTUNIUM COMPOUNDS UNDER HIGH PRESSURE
High pressure X-ray diffraction studies have been performed on NpO-2 and NpA1-2 up to 50 GPa. With NpA1-2 no phase transition is observed. An attempt to calculate the compressibility in the pressure range 0-100 GPa gives a bulk modulus B-o =65 GPa and a pressure derivative B'-o =3.5 using the Birch equation. In the case of NpO-2 we observed a gradual transition which starts at 33 GPa and is complete at 37 GPa. The high pressure phase was tentatively indexed in an orthorhombic Cmcm structure. The bulk modulus B-o =200 GPa and the pressure derivative B'-o =3.8 were determined for the low pressure phase. Similarities between NpO-2, UO-2 and ThO-2 behavior under pressure are discussed on the basis of 5f electrons delocalization.
Bibliographic Reference: ACTINIDES '85, AIX-EN-PROVENCE (FRANCE), SEPT. 2-6, 1985 WRITE TO CEC LUXEMBOURG, DG XIII/A2, POB 1907 MENTIONING PAPER E 32438 ORA
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Record Number: 1989124061000 / Last updated on: 1987-01-01
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