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The structural parameters, chemical bonding and magnetic properties of the ternary boride series M1.5Rh5.5B3 (M = Cr, Mn, Fe, Co, Ni) were investigated by first principles DFT calculations. The calculated crystallographic lattice parameters corroborate well with the experimental results of the reported Fe1.3Rh5.7B3 single crystal. In the most stable structural model used, Fe-dumbbells as well as isolated Fe-atoms exist. From spin polarised calculations, ferromagnetism is found for the members with M = Fe, Co, while ferrimagnetism is more stable for Mn1.5Rh5.5B3 and Pauli paramagnetism is more stable for M = Cr, Ni. The total magnetic moment per formula unit for the M = Mn, Fe and Co phases is calculated to be 3.32, 5.00 and 3.26 μB, respectively. According to COHP chemical bonding analysis, Rh-B contacts are mainly responsible for the structural stability, while Rh-M interactions influence the magnetic behavior of these complex borides. [ABSTRACT FROM AUTHOR]

The electronic structures of "Ti9-nFe2+nRu18B8" (n= 0, 0.5, 1, 2, 3); in connection to the recently synthesized Ti9-nFe2+n-RU18B8(n = 1, 2), have been investigated and analyzed using LSDA tight-binding calculations to elucidate the distribution of Fe and Ti, to determine the maximum Fe content, and to explore possible magnetic structures to interpret experimental magnetization results. Tbrough a combination of calculations on specific models and using tbe rigid band approximation, which is validated by the DOS curves for "T9-nFe2+nRu18B8" (n = 0, 0.5, 1, 2,3), mixing of Fe and Ti is anticipated at both tbe 2b- and 4h-chain sites. The model "Ti8.5Fe2.5Ru18B8" (n = 0.5) revealed that both Brewer-type Ti-Ru interactions as well as ligand field splitting ofthe Fe 3d orbitals regulated the observed valence electron counts between 220 and 228 electrons/formula unit. Finally, models of magnetic structures were created using "Ti6Fe5Ru18B8" (n = 3). A rigid band analysis of tbe LSDA DOS curves concluded preferred ferromagnetic ordering at low Fe content (n ⩽ 0.75) and ferrimagnetic ordering at higher Fe content (n > 0.75). Ferrimagnetism arises from antiferromagnetic exchange coupling in the scaffold of Fel-ladder and 4h-chain sites. [ABSTRACT FROM AUTHOR]

Tuning of the magnetic properties of intermetallic materials is increasingly gaining interest in the chemistry community. We report on the successful synthesis and magnetic characterizations of the two new quaternary boride series MRh6- nRu nB3 (M = Co, Ni; 1 ≤ n ≤ 5). Powder samples have been synthesized by arc-melting the elements under purified argon in a water-cooled copper crucible. The products were characterized by powder X-ray diffraction through Rietveld refinements as well as EDX measurements. All phases crystallize in the hexagonal Th7Fe3 structure type (space group P63 mc, no. 186, Z = 2). In the Co-based series, the lattice parameters decrease linearly with increasing ruthenium content, whereas in the Ni-based series they remain nearly constant for the Rh-rich side then decrease with increasing Ru content. Significant ferromagnetic interactions are observed for the Co-based series, and they decrease linearly with increasing Ru content with magnetic moments decreasing from 0.74 µB (CoRh5RuB3) to 0.13 µB (CoRhRu5B3) at 5 K and 5 T. Pauli paramagnetism dominates the Ni-based series. [ABSTRACT FROM AUTHOR]

Transition-metal borides show not only promising physical properties but also a rich variety of crystal structures. In this context, quantum-chemical tools can shed light on important facets of the chemistry within such intermetallic borides. Using density-functional theory (DFT), we analyze in detail two phases of significant structural-chemical importance: the recently synthesized Ti1+xOs2-xRuB2 and the isotypical Ti1+xOs3-xB2. Starting from the observation of different Ti/Os occupations in X-ray crystal structure analysis, we assess suitable computational models and rationalize how the interplay of Ti-Ti, Ti-Os, and Os-Os bonds drives the site preferences. Then, we move on to a systematic investigation of the metal-boron bonds which embed the characteristic, trigonal-planar B4 units within their metallic surroundings. Remarkably, the different Ti-B bonds in Ti1+xOs2-xRuB2 (and also in its ternary derivative) are of vastly different strength, and the strength of these bonds does not correlate with their length. The tools presented in this work are based on simple and insightful chemical arguments together with DFT, and may subsequently be transferred to other intermetallic phases-transition-metal borides and beyond. [ABSTRACT FROM AUTHOR]