Bond vibration is one. In crystalline materials those vibrations can produce phonons, or waves, of thermal energy. See: https://www.chemicool.com/definition/ph

Bond vibration is one. In crystalline materials those vibrations can produce phonons, or waves, of thermal energy. See: https://www.chemicool.com/definition/phonons.html https://www.chemicool.com/definition/phonons.html