  Many properties of alloyed chalcogenide glasses can be closely correlated
with the average coordination of these compounds. This is the case, for
example, of the ultrasonic constants, dilatometric softening temperature and
the vibrational densities of states. What is striking, however, is that these
properties are nevertheless almost independent of the composition at given
average coordination. Here, we report on some numerical verification of this
experimental rule as applied to vibrational density of states.
