相転移

phase transformation

[目次：結晶等(結晶構造／材料試料)]

温度、圧力、磁場などの変化によって物質が異なる状態、構造に移る現象。固体の融解、液体の気化などの第1種相転移(自由エネルギーの温度に関する1階微分が不連続になる転移)と、鉄などの強磁性体がキュリー温度で常磁性に変わったり、合金の原子配列の秩序-無秩序転移などの第2種相転移(自由エネルギーの温度に関する2階微分が不連続になる転移)がある。

A phenomenon where a substance transforms to a different state by a change of the external conditions (temperature, pressure, magnetic field, etc.). "Phase transformation" is classified into the first-order and the second-order phase transformations. The former exhibits a discontinuity in the first derivative of the free energy with respect to temperature, which includes melting of solids and vaporization of liquids. The latter exhibits a discontinuity in the second derivative of the free energy temperature, which includes the transformation of the ferromagnetic state (iron, etc.) to the paramagnetic state at Curie temperature and the transformation of the alloys from a chemical order state to a disorder state (and vice versa).

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