Volume compressibilities of actinide materials

Abstract

Using an X-ray diffractometer of the Guinier type the bulk moduli B,₀ of NpAs (NaCl structure) and of NpSn₃ (cubic AuCu₃ structure) were measured at room temperature. We find B₀ = (75.3±5.0)GPa, B₀' = (3.7 ± 1.0) for NpAs and B₀ = (72.2 ± 11.6) GPa, B₀' = (5.6 ± 4.1) for NpSn₃. Compared to the results on NpA1₂ and NpOs₂ the B₀ value for NpSn₃ is surprisingly small and supports the interpretation of high pressure Mössbauer data that this intermetallic behaves like a localized 5f electron system. In addition, we report on experimental modifications of the diffractometer which make compressibility measurements possible also at low (down to ～ 10 K) temperatures.