New ternary tantalum borides containing boron dumbbells: Experimental and theoretical studies of Ta{sub 2}OsB{sub 2} and TaRuB
- Institute of Inorganic Chemistry, RWTH Aachen University, D-52056 Aachen (Germany)
The new ternary transition metal-rich borides Ta{sub 2}OsB{sub 2} and TaRuB have been successfully synthesized by arc-melting the elements in a water-cooled crucible under an argon atmosphere. The crystal structures of both compounds were solved by single-crystal X-ray diffraction and their metal compositions were confirmed by EDX analysis. It was found that Ta{sub 2}OsB{sub 2} and TaRuB crystallize in the tetragonal Nb{sub 2}OsB{sub 2} (space group P4/mnc, no. 128) and the orthorhombic NbRuB (space group Pmma, no. 51) structure types with lattice parameters a=5.878(2) Å, c=6.857(2) Å and a=10.806(2) Å, b=3.196(1) Å, c=6.312(2) Å, respectively. Furthermore, crystallographic, electronic and bonding characteristics have been studied by density functional theory (DFT). Electronic structure relaxation has confirmed the crystallographic parameters while COHP bonding analysis indicates that B{sub 2}-dummbells are the strongest bonds in both compounds. Moreover, the formation of osmium dumbbells in Ta{sub 2}OsB{sub 2} through a Peierls distortion along the c-axis, is found to be the origin of superstructure formation. Magnetic susceptibility measurements reveal that the two phases are Pauli paramagnets, thus confirming the theoretical DOS prediction of metallic character. Also hints of superconductivity are found in the two phases, however lack of single phase samples has prevented confirmation. Furthermore, the thermodynamic stability of the two modifications of AMB (A=Nb, Ta; M =Ru, Os) are studied using DFT, as new possible phases containing either B{sub 4}- or B{sub 2}-units are predicted, the former being the most thermodynamically stable modification. - Graphical abstract: The two new ternary tantalum borides, Ta{sub 2}OsB{sub 2} and TaRuB, have been discovered. Their crystal structures contain boron dumbbells, which are the strongest bonds. Peirls distortion is found responsible for Os{sub 2}-dumbbells formation in Ta{sub 2}OsB{sub 2}. Ta{sub 2}OsB{sub 2} and TaRuB are Pauli paramagnet and potential superconductors. - Highlights: • Two new ternary tantalum borides, Ta{sub 2}OsB{sub 2} and TaRuB, discovered. • Boron dumbbells are the strongest bonds in Ta{sub 2}OsB{sub 2} and TaRuB. • Peierls distortion responsible for Os{sub 2}-dumbbells formation in Ta{sub 2}OsB{sub 2.} • Ta{sub 2}OsB{sub 2} and TaRuB are Pauli paramagnet. • Ta{sub 2}OsB{sub 2} and TaRuB contain pseudogaps and are potential superconductors.
- OSTI ID:
- 22658053
- Journal Information:
- Journal of Solid State Chemistry, Vol. 242, Issue Part 2; Other Information: Copyright (c) 2016 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
Similar Records
Nb{sub 2}OsB{sub 2}, with a new twofold superstructure of the U{sub 3}Si{sub 2} type: Synthesis, crystal chemistry and chemical bonding
Superconductivity, magnetism and structural study of some new ternary transition metal borides