Crystallization in Amorphous States of Small Organic Molecules: In Relation to Hypothetical Glass-Transition Temperatures

We have studied, by Raman and X-ray measurements, the structural change in amorphous states of benzene and its derivatives prepared by the vacuum deposition on cold substrates. It has been found that these amorphous states crystallize without passing through the supercooled-liquid state when the temperature is raised. The observed crystallization temperature Tcryst is lower than the hypothetically reported glass-transition temperature Tg. The relation between the crystallization and the glass transition in amorphous states of small organic molecules is discussed.