Disorder in the crystal structure of NaNi4(PO4)3

Abstract NaNi 4 (PO 4 ) 3 crystallizes in the space group Amam , a = 9.892(1), b = 14.842(2), and c = 6.3576(2) A. For Z = 4, the calculated density is 3.862 g/cm 3 ( V = 933.3A 3 ). The presence of several weak reflections (of the class 2 k 0 and 6 k 0) which should be systematically absent in this space group has been attributed to a partial disorder of one of the phosphate tetrahedra. Two half-occupied P (2) sites related by a mirror normal to the a axis result in a column of phosphate tetrahedra pointing either up or down in this direction. Nickel atoms occupy five- and six-coordinated sites while sodium is six-coordinated.