The spectroscopically observable tris(thiolate) complex [Ru(dppbt)3](+) (1(+)) (dppbt = diphenylphosphinobenzenethiolate) is reported to have chemistry based on thiyl-radical character. High-level ab initio methods predict the ground-state electronic structure of 1(+) to be an open-shell diradical singlet state with antiferromagnetic coupling between (S = 1/2) Ru(III) and (S = 1/2) S pz, rather the previous description based on a diradical state involving two S p orbitals. These new results provide an improved understanding of the experimental chemistry of 1(+) and related species.
Detailed first-principles density functional theory (DFT) computations were performed to investigate the geometries, the electronic, and the magnetic properties of both armchair-edged silicon carbide nanoribbons (aSiCNRs) and zigzag-edged silicon carbide nanoribbons (zSiCNRs) with Stone-Wales (SW) defects. SW defects in the center of aSiCNRs can remarkably reduce their band gaps, irrespective of the orientation of the defect, whereas zSiCNRs with SW defects in the center or at the edges exhibit degenerate energies of their ferromagnetic (FM) and antiferromagnetic (AFM) states, in which metallic and half-metallic behavior can be observed, respectively; half-metallic behavior can even be observed in both the FM and AFM states simultaneously. Further, it was shown that the formation energies of the SW defects in SiCNRs are orientation dependent, and the formation of edge defects is always favored over the formation of interior defects in zSiCNRs. The possible existence of SW defects in SiCNRs was further validated through exploring the kinetic process of their formation. These findings can be anticipated to provide valuable information in promoting the potential applications of SiC-based nanomaterials in multifunctional and spintronic nanodevices.
Based on first-principles computations, the geometries, stabilities, electronic and magnetic properties of fully and partially hydrogenated silicon carbide nanoribbons (SiCNRs) were investigated. Independent of the ribbon width, the fully hydrogenated zigzag and armchair SiCNRs are all non-magnetic wideband-gap semiconductors. By hydrogenating zigzag SiCNRs (zSiCNRs) from the edge(s) step by step, we have constructed partially hydrogenated zSiCNRs that can be viewed as the combination of hydrogenated and pristine zigzag SiC chain building blocks along the periodical direction. The computed results reveal that greatly enriched electronic and magnetic properties can be achieved in zSiCNRs: the transition of the antiferromagnetic spin gapless semiconductor (SGS)-ferromagnetic metal-antiferromagnetic half-metal-non-magnetic semiconductor can be achieved by controlling the hydrogenation pattern and ratio. Notably, this is the first time that the concept of successive hydrogenation starting from the edge(s) is proposed as an effective approach to fine-tune the electronic and magnetic behaviors of SiCNRs. These appealing features, especially the diverse electronic and magnetic transitions, in the unitary SiCNR-based nanostructures may provide tremendous potential applications for integrated multi-functional and spintronic nanodevices.
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