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Peierls‐Distorted Ru‐Chains and Boron Dumbbells in Nb 2 RuB 2 and Ta 2 RuB 2 from First‐Principles Calculations and Experiments
Author(s) -
St. Touzani Rachid,
Mbarki Mohammed,
Chen Ximeng,
Fokwa Boniface P. T.
Publication year - 2016
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.201600689
Subject(s) - superstructure , chemistry , crystallography , crystal structure , transition metal , type (biology) , single crystal , x ray crystallography , diffraction , ecology , biochemistry , oceanography , physics , optics , biology , geology , catalysis
Nb 2 RuB 2 and Ta 2 RuB 2 phases were recently predicted by GGA‐VASP structure optimization to crystallize in the Nb 2 OsB 2 ‐type structure. Although the Fe‐based (Mo 2 FeB 2 type) and Os‐based (Nb 2 OsB 2 type, superstructure variant of Mo 2 FeB 2 type) analogues have been synthesized and characterized successfully, the Ru‐based phases remained unknown. Crystal structure prediction of Nb 2 RuB 2 and Ta 2 RuB 2 phases, using an evolutionary algorithm, led to the AlMn 2 B 2 ‐type structure in contrast to the aforementioned optimization; however, phonon calculations showed that the Nb 2 OsB 2 ‐type phases are dynamically more stable than the AlMn 2 B 2 ‐type phases. A slightly modified synthetic strategy finally led to the successful preparation of the predicted phases. The extremely quick arc‐melting procedure, under argon atmosphere, not only led to a quantitative amount of the phases but also to single crystals suitable for structure determination. Powder and single‐crystal X‐ray diffraction as well as EDX analysis of the metal ratio have confirmed the GGA‐VASP structure optimization: Nb 2 RuB 2 and Ta 2 RuB 2 compounds indeed crystallize isotypically with Nb 2 OsB 2 structure, a superstructure variant of Mo 2 FeB 2 type, in which B‐dumbbells and Peierls‐distorted Ru‐chains are found. Susceptibility measurements on a Ta 2 RuB 2 single crystal reveal no superconducting transition down to 2 K, even though some features in the band structures of both phases, similar to those reported in superconducting NbRuB, hinted at possible superconductivity.