  Results on the dynamics of silica are presented: vibrations and relaxations.
Using molecular dynamics, glass structures are generated by rapidly quenching
melts below the glass transition. For the local minima of the structures the
vibrational density of states is determined, the structures of the eigenmodes
are analyzed, and the influence of the single components is discussed.
Relaxations are studied in both amorphous SiO$_2$ and silica melts. Our main
focus is on the type of relaxation, i.e., whether the main contributions are
caused by small atomic displacements, or by bond-breaking processes, e.g.
creation and annihilation of dangling bonds. The eigenvector of the relaxations
is found to be similar to the low-frequency one.
