Netsu Sokutei, 28 (5), p. 200, (2001)


熱容量 2. 格子振動

Heat Capacity 2. Lattice Vibration

格子振動の熱容量への寄与について解説した。調和近似の範囲では格子振動によ る熱容量の理解はフォノン状態密度の理解と同義である。デバイモデルを越えるには 結晶の周期性を利用して格子振動計算を行なう。1次元結晶について計算法を詳述 し,現実の3次元結晶への拡張について説明した。格子熱容量解析のいくつかの実例 を示すと共に,格子熱容量に関わる今後の課題についても簡単に紹介した。
Vibrational contribution to heat capacity of solid is explained. The Debye model is introduced through semi-classical consideration. It is emphasized that the Debye model does not assume the isotropy of solid. Lattice dynamical calculation of phonon density of states is described within a harmonic approximation for a 1-dimensional crystal in detail. Application to molecular solids is outlined while assuming the use of the atom-atom potential method. Some examples are described of utilization of lattice dynamical calculation and of analysis of lattice heat capacity. Briefly commented are advanced topics of lattice heat capacity, including localization of vibration and low-energy excitation in disordered system, anharmonic cases, and phason contribution in incommensurately modulated system.