Crystal chemistry of M1-M2-H-Arsenates und -Vanadates

The project aims are the low-temperature hydrothermal synthesis, structural characterisation and crystal-chemical and topological classification of novel protonated and/or water bearing M1-M2-arsenates and vanadates (M1 = Sr 2+, Cd2+, Ba2+, Bi 3+; M2 = Mg 2+, Mn 2+,3+, Fe2+,3+, Co2+, Ni2+, Cu2+, Zn2+). These compounds are of great interest with respect to their physicochemical properties (e.g., catalytic, absorption, zeolitic and ion conductivity properties, as well as luminescence). A detailed study of this class of compounds has never been undertaken so far, but preliminary investigations have demonstrated that several novel compounds exist, with some of them crystallising in new structure types. The chemical variability of the existing hydrogen arsenates and vanadates of mostly divalent metals is large. However, judging from the complex chemical compositions of the few presently known natural and synthetic members (only 16 compounds, among which eleven arsenates and five vanadates), it is expected that the chemical variability of these compounds is distinctly larger than known at present. Among the 16 presently known compounds, a total of five have been synthesised within preliminary investigations of the applicant. There is only one Cd representative known so far. It is therefore evident that the possibility to synthesise new compounds with interesting crystal-chemical features within this group is enormous. Preliminary experiments of the applicant have demonstrated that newly synthesised compounds either belong to already known structural families or they represent new structure types with previously unknown M1:M2 ratios and unprecedented topologies. The major aim of the project is to unravel the complex mechanisms and factors of symmetry adoption within M1-M2-H-arsenates and vanadates by comparative analysis of results known from the literature as well as from newly synthesized compounds. This will provide an important basis for investigation of the reasons for the observed varieties of the individual topologies, structure types and M1:M2 ratios, and their prediction.