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Alexander G. Shtukenberg, Harald Euler, Armin Kirfel, Dmitry Yu. Popov
Symmetry reduction and cation ordering in solid solution of stronium-lead and barium-lead nitrates
Keywords: Kinetic ordering of atoms, Strontium nitrate, Barium nitrate, Lead nitrate
Kinetic ordering of the cations in (Sr,Pb)(NO3)2 and (Ba,Pb)(NO3)2 solid solutions with anomalous birefringence was studied by means of single crystal X-ray diffraction. The crystal structures of two samples of (Sr0.62Pb0.38)(NO3)2 and (Ba0.20Pb0.80)(NO3)2, respectively, taken from the {111} growth sectors as well as of two samples of (Sr0.62Pb0.38) (NO3)2 taken from the {100} growth sector were refined in the ideal structure space group Pa-3 and in two of its subgroups – trigonal R-3 and triclinic P-1 with R = 0.009 — 0.027. The final choice of trigonal symmetry for the samples from the {111} growth sectors is based on the analysis of the diffraction patterns and of the cation distributions over the crystallographic sites, which reflects the different orientations of the cation coordination polyhedra with respect to the (111) growth face (cubic setting). The observed optical indicatrices were successfully reproduced in the point-dipole approximation.
Zeitschrift für Kristallographie, Oldenbourg Wissenschaftsverlag
Print ISSN: 0044-2968
Volume: 221, 10/2006
Pages: 681 - 688