A theoretical model is proposed for the synthesis of new quasicrystalline phases derived from the s-phase, CrFe. The s-phase can be described as a tiling of squares and triangles, each tile a full cell of the Cr3Si- or half cell of the Al3Zr4-type respectively. While squares and triangles can tessellate simply and periodically, quasicrystalline tilings represent a captivatingly complex alternative with chemical origins. Chemical pressure calculations reveal insertion of silicon into this structure creates high, positive pressures at silicon sites, suggesting the atom is too large for its surroundings. Formation of dodecagonal clusters provides a means of coping with this pressure. These results are supported by the observation of VMn7Si2, a structure recently solved from powder diffraction data by Iga et al., and confirmed in our lab from single crystal structural analysis.  Preliminary synthetic explorations in search of dodecagonal phases in other ternary transition metal-silicide systems are also described.

Theoretical framework toward targeted synthesis of new dodecagonal quasicrystals and quasicrystalline approximants

244th National Meeting (2012)

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