Structure cristalline d'un conducteur metallique bidimensionnel: le bronze violet de potassium et molybdene K/sub 0. 9/Mo/sub 6/O/sub 17/

Journal Article · Tue Mar 15 04:00:00 EST 1983 · J. Solid State Chem.; (United States)

DOI:https://doi.org/10.1016/0022-4596(83)90050-6· OSTI ID:5728431

Vincent, H ^[1]; Ghedira, M; Marcus, J; Mercier, J; Schdenker, C

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1. Laboratoire de Cristallographie C.N.R.S., Cedex, France

Single crystals of the purple bronze K/sub 0.9/Mo/sub 6/O/sub 17/ have been grown by a electrolytic reduction technique. Measurements of the electrical resistivity show that this compound is a quasi two-dimensional metal. A crystal structure determination is used to explain the strongly anisotropic resistivity. K/sub 0.9/Mo/sub 6/O/sub 17/ is found to be trigonal with lattice parameters: a=5.538 angstrom and c=13.656 angstrom; Z=1. The space group is P3. The K cations are surrounded by 12 oxygen anions which form icosahedral sites. One third of the Mo cations (Mo(1)) occupy tetrahedral sites, while the Mo(2) and Mo(3) cations have octahedral surroundings. The structure can be described as slabs of ReO/sub 3/-type connected by KO/sub 12/ icosahedra. Each slab is built up of 4 layers, parallel to the (001) plane, of Mo(2) and Mo(3) octahedra sharing corners. Two slabs are connected by K icosahedra which share 2 faces with the upper and lower neighboring Mo(3) octahedra. Each K icosahedron is edge linked to 3 upper and 3 lower Mo(1) tetrahedra. Each Mo(1) tetrahedron is itself corner linked to 3 Mo(3) octahedra of the neighboring layer. The deformations of the occupied polyhedra are a good illustration of the Pauling's third rule. There is no Mo(1)-O-Mo(1) bonding, so that the Mo-O-Mo bonding, infinite in the a and b directions, is disrupted in the c direction. The Zachariasen's bond length-bond strength relation has been applied to the Mo-O bonds. The computed effective mean Mo valences are +6 for Mo(1) on tetrahedral sites and about 5.1 and 5.8, respectively, for Mo(2) and Mo(3) on octahedral sites. The 4d electrons of Mo atoms are so located in the two-dimensional infinite slabs of octahedra.

• OSTI ID: 5728431
• Journal Information: J. Solid State Chem.; (United States), Journal Name: J. Solid State Chem.; (United States) Vol. 47:1; ISSN JSSCB
• Country of Publication: United States
• Language: French

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKALI METAL COMPOUNDS
ANIONS
ANISOTROPY
BOND LENGTHS
CATIONS
CHALCOGENIDES
CHARGED PARTICLES
CHEMICAL BONDS
CHEMICAL REACTIONS
CRYSTAL STRUCTURE
CRYSTALS
DIMENSIONS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTROLYSIS
IONS
LATTICE PARAMETERS
LENGTH
LYSIS
MOLYBDENUM COMPOUNDS
MOLYBDENUM OXIDES
MONOCRYSTALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POTASSIUM COMPOUNDS
POTASSIUM OXIDES
REDUCTION
STRUCTURAL CHEMICAL ANALYSIS
TRANSITION ELEMENT COMPOUNDS