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Competing Electronic and Size Effects When Substituting 3d Elements for Nb in Nb 3 Ru 5 B 2 En Route to the Quaternary Phases (Nb 2– x Sc x ) 4 g Nb 2 a Ru 5 B 2 (1 ≤ x < 2), Nb 3– x M x Ru 5 B 2 (M = Ti, V; x ≈ 1), and Nb 2+ x M 1– x Ru 5 B 2 (M = Cr, Mn, Fe, Co, Ni; 0 < x ≤ 0.5)
Author(s) -
Hermus Martin,
Fokwa Boniface P. T.
Publication year - 2012
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201200627
Subject(s) - tetragonal crystal system , niobium , crystallography , chemistry , valence (chemistry) , ruthenium , crystal structure , valence electron , crystallite , ternary operation , electron , biochemistry , physics , organic chemistry , quantum mechanics , computer science , programming language , catalysis
Abstract Single crystals and polycrystalline samples of (Nb 2– x Sc x ) 4 g Nb 2 a Ru 5 B 2 (1 ≤ x < 2), Nb 3– x M x Ru 5 B 2 (M = Ti, V; x ≈ 1), and Nb 2+ x M 1– x Ru 5 B 2 (M = Cr, Mn, Fe, Co, Ni; 0 < x ≤ 0.5) were synthesized from the elements and characterized by single‐crystal and powder X‐ray diffraction as well as energy‐dispersive X‐ray analysis. These phases are substitutional variants of the recently reported Nb 3 Ru 5 B 2 phase and crystallize in the Ti 3 Co 5 B 2 ‐type structure (tetragonal, space group P 4/ mbm , no. 127). The structure consists of layers of ruthenium atoms that build trigonal, tetragonal, and pentagonal prisms, in which the other atoms are incorporated. The larger 3d metals, Sc, Ti, and V are found on the larger pentagonal prisms, together with niobium, and also (except for Sc) on the tetragonal prisms. The smaller 3d metals, Cr–Ni, are only found on the tetragonal prisms, but also mix with niobium. DFT calculations on the ternary phase Nb 3 Ru 5 B 2 suggested that the reason for this site mixing can be found in its electronic structure and the application of the rigid band model proposed a valence electron (VE) range between ca. 58 and 64 for the derived stable phases. All synthesized quaternary phases fit very well within this VE range.