In the natrochalcite-type compounds NaCu2(H3O2)(SO4)2 and RbCu2(H3O2)(SeO4)2 the lengths of the two different hydrogen bridges vary widely: 2.44 Å and 2.70 Å in the Na-S member, and 2.60 Å and 3.03 Å in the Rb-Se member. Both structures were refined by single-crystal neutron diffraction methods. Least-squares refinements (harmonic vibrations for all atoms) resulted in a splitting of the H atom positions of the short bridges by 0.265(13) Å in the Na-S member, and by 0.472(6) Å in the Rb-Se member. In the two compounds no clear evidence for an ordering of the split position of the H atom was found.
Zeitschrift für Kristallographie – Crystalline Materials offers a place for researchers to present results of their crystallographic studies. The journal includes theoretical as well as experimental research. It publishes Original Papers, Letters and Review Articles in manifold areas of crystallography.