Neutron refinements of NaCu2(H3O2)(SO4)2 and RbCu2(H3O2)(SeO4)2: variation of the hydrogen bond system in the natrochalcite-type series

NaCuz(H30Z)(S04h / RbCuz(H)Oz)(Se04h / Natrochalcite-type compounds / Hydrogenbondsin H30Z configuration Abstract. In the natrochalcite-type compounds NaCuz(H30z)(S04h and RbCuz(H30z)(Se04h the lengths of the two different hydrogen bridges vary widely: 2.44 A and 2.70 A in the Na-S member, and 2.60 A and 3.03 A 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) A in the Na-S member, and by 0.472(6) A 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.