What is the role of phonon energy in different glasses? What is the significance of low and high phonon energy in the different glassy system?
sir can you tell me which glass is more appropriate for greater quantum efficiency and why ? if the glass have lower quantum efficiency that means in this relaxation process will be weak or it is not possible ?
Thanks. How we calculate the phonon energy for a particular system ( like borate ; phosphate ; tellurite ; chalcogenide ; vanadate glasses )
As Lothar said before. We usually takes this value from the Raman spectra. For example, if you see the Raman spectrum of a tellurite glass you will se that the maximum Raman peak is around 750 cm-1. So you can consider this as the maximum phonon energy of that glass.
Just entered the question,
my problem is the definition of phonons in an amorphic material like glas. I´ve learned, that the production of phonons is restricted to lattice structures. Roberto, could you help me to understand your remarks.
Hanno, I understand your problem and I have never seen its clarification. Here is my own version:
For any finite set of masses and springs, no matter how irregular, we can find its eigenfrequencies, right? This is what is called phonons (usually). But you probably expect some relation with reciprocal lattice? Well, the reciprocal lattice is more or less the Fourier transform of primary lattice nodes. Thus exactly the same qualitative picture may be obtained considering irregular set of atoms, just like it takes place in glasses. The bad news is that when going to infinite glass we obtain not a discrete but continuous set of reciprocal lattice points (k-vectors). As the distances between real atoms cannot be arbitrarily small, then such k-spectrum should be bounded, even in infinite glass. Therefore we can talk about the maximum energy of mechanical vibrations in glasses ("phonons"). In this picture, however, there is no place (at least I can't see it) for microscopic polarization of such "phonons".
Can anyone send good paper related to these topics, where these things are explained.
Dear Hanno
It is clear that in crystal structure the phonon energy is related to the lattice vibration and we know that the periodicity will take a long range order in a crystal structure, but the lattice vibration will also occur for the amorphous structure because the structure will take a short range order of the periodicity, this mean that the lattice vibration will produced by the short rang of periodicity.
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