Lattice vibration

Japanese: 格子振動 - こうししんどう（英語表記）lattice vibration

A vibration that occurs in the vicinity of the stable positions of the atoms and molecules that make up the crystal lattice propagates as a wave within the crystal. Lattice vibrations are broken down into characteristic vibrations specified by the wave vector. As the wave vector approaches zero, i.e., as the wavelength becomes longer, the vibrations whose frequency approaches zero correspond to sound waves and are called acoustic modes. In crystals that contain two or more types of atoms, in addition to acoustic modes, there exist characteristic vibrations with large frequencies even when the wave vector approaches zero, and these are called optical modes because they are easily excited by light. When lattice vibrations are quantized, they become quasiparticles called phonons. They are studied using infrared absorption and neutron diffraction.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

結晶格子を構成している原子や分子が，それらの安定な位置の付近で行う振動で，結晶内を波として伝わる。格子振動は波数ベクトルで指定される固有振動に分解される。波数ベクトルが零に近づく，すなわち長波長になると振動数が零に近づく振動は音波に相当し音響モードと呼ばれる。2種以上の原子を含む結晶では，音響モード以外に波数ベクトルが零に近づいても大きな振動数をもつ固有振動が存在し，これは光によって励起されやすいので光学モードと呼ばれる。格子振動を量子化するとフォノンと呼ばれる準粒子になる。赤外線吸収や中性子回折などによって研究される。

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