長周期構造

long period structure

[目次：結晶等(結晶構造／材料試料)]

たとえばCuAuⅠでは、規則格子が5個並び、次に逆位相のずれ(格子の半分のずれ)をもつ規則格子が5個並び、全体として元の格子の10倍の単位の構造が作られる。このように元の格子に比べて長い周期の構造を長周期構造という。CuAuⅠでの長周期相は規則相と不規則相の間のわずかな温度範囲に出現する。電子回折図形には規則相の反射が分裂して、10倍の周期に対応する位置に回折斑点が現れる。長周期構造は金属間化合物やSiCに現れる。

For example, in the phase of CuAuⅠ, five ordered lattices are aligned in a direction followed by another five ordered lattices with an anti-phase shift to the former lattices, resulting into formation of a structure with a unit of 10 times larger than the original lattice. Such a structure is called a "long period structure." The phase CuAuⅠ appears in a narrow temperature range between the ordered phase and the disordered phase. In a diffraction pattern, the reflections from the ordered phase split to diffraction spots appearing at the positions corresponding to a period of 10 times that of the ordered phase. Long period structures appear in intermetallic compounds and SiC.

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