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User:Benjah-bmm27/degree/3/NLA

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Chemistry of solids, NLA

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Bonding and electronic structure in solids

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Metallic conductivity in transition metal oxides

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  • Non-stoichiometry
  • The monoxides MO have the rocksalt structure
    • TiOx (0.7 > x > 1.25) and VO are metallic conductors
      • overlap of t2g 3d orbitals from neighbouring Ti(II) atoms results in a t2g conduction band
    • MnO and NiO are insulators because their t2g 3d orbitals are too contracted to overlap due to the greater electronegativity of Mn and Ni
    • FeO and CoO are also insulators, whereas second and third row transition metal oxides are more commonly metallic conductors
  • Electrical conductivity in transition metal dioxides
  • Electrical conductivity in transition metal trioxides
    • ReO3 — Re(VI) is d1, lustrous red metallic conductor
      • High oxidation state Re so direct d-d orbital overlap very unlikely — partially filled π-band arises from Re(5d)-O(2p) overlap
    • WO3 — W(VI) is d0, insulator
    • NaxWO3 — W(V) is d1, gold-coloured metallic conductor

Semiconductors

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Defects and non-stoichiometry

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Superconductors

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