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V. Levytskyy, V. Babizhetskyy, B.Ya. Kotur, H. Michor, O. Isnard:
"Crystal Chemistry of Ternary Rare Earth Transition Metal Carbides: Recent Studies";
Vortrag: SCTE2018, The 21st International Conference on Solid Compounds of Transition Elements, Wien (eingeladen); 25.03.2018 - 29.03.2018.

A brief critical overview will be presented on ternary rare earth - transition element - carbon systems and their compounds. Main attention will be devoted to recent studies of crystal structure peculiarities of ternary carbides. More than 400 ternary phases have been found up to now, 45 of which in past 10 years. In total, they
represent a variety of 50 structure types. Three species of carbon arrangement occur in these structures: isolated C atoms, C₂ pairs and C₃ chains. All known structure types of these ternary carbides are classified into two groups: metal-rich carbides (intermetallics) and carbometalates∗. Conditional division into these groups is performed depending on the carbon content and the M/C ratio (M = metal atoms). In the latter group, complex anions [TyCz]^n- forming clusters of different dimensionality are identified as the key structure building elements of these compounds. The presence of covalent T-T interactions in [TyCz]^n- clusters was recently confirmed by ⁵⁷Fe Mössbauer spectra of R₁₅Fe₈C₂₅ compounds+. Two series of novel compounds, R₂Mn₂C₅ and R₂CoC₂, with novel structure-types as well as new representatives of earlier known structure types have been investigated in this work. From the analysis of crystal structure data we estimate some physical properties and the valence states of elements in these compounds. Crystal structure relations with chemical reactivity are discussed. The broad diversity of unusual topologies has rendered these compounds of great interest for experimental as well as theoretical chemistry, and also with respect to their electronic and physical properties.
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∗ E. Dashjav et al., J. Solid State Chem. 180 (2007) 636-653
+ B. Davaasuren et al, J. Solid State Chem. 225 (2015) 450-454