Available online 25 May 2002.
Abstract
The influence of metal-metal bonding on the physical properties of the titanium and vanadium monosulfides, monoselenides, and their solid solutions is explored. Compounds were synthesized at 800°C and characterized by room-temperature X-ray diffraction, chemical analysis, density, differential thermal analysis (DTA), magnetic susceptibility, and electrical resistance. All compounds formed one of three closely related crystal structures: hexagonal B 81, orthorhombic B31, or a rhombohedral 9Rpolytype. In all these structures, partially occupied orbitals of 3d parentage form narrow bands as a result of metal-metal interactions; all compounds were metallic and Pauli paramagnetic except nominal VSe, which exhibits an antiferromagnetic Néel temperature TN ≅ 240 K and becomes semiconductive below 50 K. Evidence of anion vacancies was found for all samples; compounds formed from larger selenium atoms also incorporate interstitial metals into trigonal bipyramidal sites, stabilizing the hexagonal B81 structure and avoiding distortions to the ideal ("unstuffed") B31 or 9Rstructures.
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