Re4Si7, First in a New MoSi2-Based Family of 14-Electron Phases

• The compound Re4Si7 poses a long-standing structural mystery at the intersection of the quantum chemical and material properties areas of interest. Its atomic structure has gradually emerged over X-ray and electron diffraction studies since 1941 to be a complex ordering of Si vacancies on a MoSi2-type lattice, the details of which remain unresolved. In 1941, it was originally identified as ReSi2, adopting the MoSi2-type crystal structure (Figure 1).1a In this structure, Re atoms form a body-centered tetragonal lattice, while the Si atoms lie in the square-pyramidal interstitial spaces of this Re lattice. This was followed by two structure reports in progressively lower symmetry: an orthorhombic Immm solution (1983),1b and a triclinic P1 solution (1995),1c in which fractional occupancies on the Si sites adjust the composition to the Re4Si7 stoichiometry reported in a redetermination of the Re–Si phase diagram.1d Electron microscopy investigations then revealed complex superstructures and incommensurability in Re4Si7 samples.2 This work culminated in an attempt to solve its structure as an eight-fold supercell in the space group Cm from single-crystal synchrotron X-ray diffraction data (2004).1e Severe refinement instabilities were encountered, and the published structure shows chemically implausible Re–Si and Si–Si distances

Ämnesord

NATURVETENSKAP  -- Kemi -- Oorganisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Inorganic Chemistry (hsv//eng)

Nyckelord

bond theory

electron localizability indicator

intermetallic phases;solid-state structures

transition-metal silicides

Inorganic chemistry

Oorganisk kemi

Inorganic Chemistry

oorganisk kemi

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