Neutron-diffraction studies ofUBe13andThBe13

Abstract

Neutron-diffraction measurements have been made on polycrystalline samples of ${\mathrm{UBe}}_{13}$ and ${\mathrm{ThBe}}_{13}$ at several temperatures between 10 and 250 K. Refinement of the powder patterns using the Rietveld method of profile analysis yields structural parameters in substantial agreement with previous work [space group $O_g^6$ (Fm3c); 8 U in 8(a); 8 Be(I) in 8(b); 96 Be(II) in 96(i)]. Values for the (y,z) coordinates of the 96 Be(II) are (0.1763, 0.1150) and (0.1745, 0.1129) for ${\mathrm{UBe}}_{13}$ and ${\mathrm{ThBe}}_{13}$, respectively. They correspond very closely to those values required for regular snub-cube coordination of the Be(II) around the uranium atoms.