Phonon scattering
= Phonon scattering
<Phonon scattering> changes the occupation or propagation of lattice-vibration <normal modes> through interactions with boundaries, defects or other <phonons>. Anharmonic terms permit phonon-phonon scattering. Different processes need not relax heat flow equally: normal processes conserve total <crystal momentum> within the first <Brillouin zone>, whereas <Umklapp scattering> changes its representative by a nonzero <reciprocal lattice> vector.