Phonons are quantized lattice vibrations. They are travelling waves of the form(adsbygoogle = window.adsbygoogle || []).push({});

exp(ikr) taken to satisfy periodic boundary conditions. I'm guessing periodic boundary conditions are equivalent to demanding the waves to be zero at the boundary. which is what characterizes standing waves (right? :S)

So are all phonons really just the number of possible standing waves you can form from the solutions exp(ikr).

And if so, how is one to interpret phonon-phonon collisions? What happens physically when two standing wave vibrations collide and why can we speak of conservation of the crystal momentum?

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# Phonon collision and more

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