The synthesis and crystal structures of the first rare-earth alkaline-earth selenite chlorides MNd10(SeO3)(12)Cl-8 (M = Ca and Sr)

Two new alkaline-earth Nd selenite chlorides MNd10(SeO3)(12)Cl-8 (M = Ca, Sr) were obtained using crystal growth from alkaline-earth chloride melts in quartz tubes. These new compounds crystallize in the orthorhombic system in space group C cca (# 68). The compounds were studied by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction. It was shown that both compounds adopt the same structure type, constructed by complex [M-11(SeO3)(12)](8+) slabs separated by chloride anion layers perpendicular to the longest cell parameter. The SeO3 groups show a pyramidal shape and may be described as SeO3E tetrahedra. Such SeO3 groups decorate the Nd-O skeletons forming the [M-11(SeO3)(12)](8+) slabs. (C) 2007 Elsevier Inc. All rights reserved.