OD (order-disorder) character of the crystal structure of maucherite Ni (sub 8) As (sub 11)

Maucherite Ni (sub 11) As (sub 8) has been found to be an OD (order-disorder) structure consisting of unit layers, which display stacking orientation disorder. Maucherite is composed of OD layers of one kind, with layer symmetry P(4)m2 (the bracketed element is perpendicular to the layer), the simplest, uniform stacking of which can result either in a tetragonal MDO1 structure with space-group type P4 (sub 1) 2 (sub 1) 2 or in a monoclinic MDO2 structure with space-group type C2/c. Beside these, polytypes with more complicated or disordered stacking sequences may form.