Structural stability of an icosahedral Cd-Yb quasicrystal and its crystalline approximant under high pressure

Cd-Yb準結晶及び近似結晶の高圧下構造安定性

綿貫 徹; 佐藤 卓*; Tsai, A. P.*

Watanuki, Tetsu; Sato, Taku*; Tsai, A. P.*

Cd-Yb準結晶とその近似結晶、及び同型構造を持つCd-Eu合金について高圧下における構造安定性を調べた。放射光による回折実験をヘリウム圧力媒体を用いた静水圧条件下で40GPaまで行った結果、それらの正二十面体格子あるいはbcc格子が高圧でも安定であることが明らかとなった。周期,準周期によらず安定であったことは、それらを構成する原子クラスターの性質による、特に、その中心対称充填構造が低対称変形を阻害し、格子変形も生じなかったものと考えられる。

Synchrotron X-ray powder diffraction studies on an icosahedral Cd-Yb quasicrystal (iCd-Yb), its crystalline approximant of CdYb (cCd-Yb) and the related CdEu (cCd-Eu) material were performed under pressures of up to about 40 GPa at room temperature. The icosahedral lattice of the atomic cluster in iCd-Yb and the bcc lattices in cCd-Yb and cCd-Eu were found to be stable under pressure. Although the Tsai-type atomic cluster can possibly be distorted in various ways, low-symmetry distortion modes do not seem to develop even at high pressure. It is considered that the cluster structure of centrosymmetric dense atomic packing prevented low-symmetry distortions and consequently provided the cluster lattice stability.