Order-Disorder Phase Transitions in Quasicrystals

Hiroshi ABE: Diffuse Scattering from Quasicrystals: Static and Dynamic Fluctuations

Atomic short-range order (SRO) relating to a phason is key to resolve phase stabilities in Al-Ni-Co decagonal quasicrystals. Complicated SRO was determined by anomalous X-ray scattering. At the same time, anisotropic distributions of diffuse scattering appeared around Bragg reflections. Moreover, the anomalous Debye-Waller factor was seen in an order-disorder phase transition at high temperature.

	図1　ＨＢＳ(Hexagon-Boat-Star)タイリング。(HBS tiling).
	図2　フィボナッチ格子.ランダムフェイゾンによって原子フリップが起きる。(Fibonacci lattice. Atomic flips are caused by a random phason.)
	図3　Al₇₀Ni₁₅Co₁₅ の反射の動径方向の散乱強度。(a) 8. 304keV、(b) 8.098 keV. (Diffuse scattering along the radial direction around Bragg reflection. (a) 8.304 keV, (b) 8.098 keV).
	図4　 Al₇₂Ni₂₀Co₈ の反射の動径方向の散乱強度。(a) 8. 304keV、(b) 8.098 keV. (Diffuse scattering along the radial direction around Bragg reflection. (a) 8.304 keV, (b) 8.098 keV).
	図5　ブラッグ反射の半値幅の\|G^⊥\|依存性.( \|G^⊥\| dependence of full width at half maximum of Bragg reflections).
	図6　積分強度比の(a)\|G^\|\|\|依存性と(b)\|G^⊥\|依存性。((a)\|G^\|\|\| dependence, (b)\|G^⊥\| dependence of a ratio of integrated intensities of Bragg reflections).
	図7　ランダムフェイゾンとＳＲＯの関係。(Schematic diagram of random phason and Short-range order).

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