Nature of the first diffraction peak in glassy selenium.

The physical signi6cance of the 6rst di8'raction peak in glassy Se is discussed in the light of recent experimental results regarding the temperature dependence of the parameters characterizing the first peaks in the elastic S(Q, u = 0) and static S(Q) structure factors. The rather different behavior with temperature of both peaks as well as a comparison with the behavior observed for a polycrystalline (trigonal) sample serves to clarify their relationships with physical magnitudes such as thermal-expansion coeKcients arid temperature-dependent correlation lengths.