The crystal structure of americium(III) oxybromide

Abstract

Americium (III) oxybromide has been prepared by vapor phase hydrolysis of americium (III) bromide, which in turn was obtained by hydrobromination of Am (OH) 3 in a stream of HBr at 590°C. The structure was evaluated from powder patterns. AmOBr crystallizes in a tetragonal PbFCl-type structure, space group P4/ nmm- D 4 h 7, with a = 3.982 A ̊ , c = 7.644 A ̊ , c a = 1.920 and V = 121.2 A ̊ 3 . With Z = 2 formula units per unit cell, the density was calculated as 9.23 g cm −3. There are 2 Am atoms in (0,0, u 1) and ( 1 2 , 1 2 , u ̄ 1 ), 2 O atoms in ( 1 2 , 0, 0) and (0, 1 2 , 0), and 2 Br atoms in (0, 0, u 2 ) and ( 1 2 , 1 2 , u ̄ 2 ) The parameters were found to be u 1 = 0.1789 ±0.0080 and u 2 = 0.6183 ± 0.0206. The interatomic distances are Am-O = 2.415 A ̊ and Am-Br = 3.36 and 3.210 Å.