Viscous liquids and the glass transition. VI. Relaxations in simple molecule glasses in the 4–77 K range

Publisher Website
Google Scholar
Abstract
Previous dielectric studies from our laboratory have shown that a secondary relaxation β, usually attributed to molecular flexibility, occurs as often, with the same strength, and in the same place (0.75 Tg for 1 kHz measuring frequency) in glasses made of simple rigid molecules. We concluded that the β relaxation is a universal feature of amorphous packing. We have now extended our previous studies on molecular and fused salt glasses to the 4–77 K temperature range, and found relaxations at about 0.2–0.5 Tg in seven of 16 substances examined. These low temperature relaxations appear in some rigid molecule and in some flexible molecule glasses, but not all. We conclude flexibility is not a necessary condition for a low temperature relaxation, but feel the evidence that such relaxations are also characteristic of amorphous packing is weak. Four alcohols studied gave evidence of an additional loss peak below 4 K. We suggest this peak may be related to the well‐known very low temperature anomalies common to most glasses. A general explanation of secondary relaxations in glasses in terms of the amorphous cluster model of glass structure is proposed.