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  • Title: Hiking down the energy landscape: progress toward the Kauzmann temperature via vapor deposition.
    Author: Kearns KL, Swallen SF, Ediger MD, Wu T, Sun Y, Yu L.
    Journal: J Phys Chem B; 2008 Apr 24; 112(16):4934-42. PubMed ID: 18386872.
    Abstract:
    Physical vapor deposition was employed to prepare amorphous samples of indomethacin and 1,3,5-(tris)naphthylbenzene. By depositing onto substrates held somewhat below the glass transition temperature and varying the deposition rate from 15 to 0.2 nm/s, glasses with low enthalpies and exceptional kinetic stability were prepared. Glasses with fictive temperatures that are as much as 40 K lower than those prepared by cooling the liquid can be made by vapor deposition. As compared to an ordinary glass, the most stable vapor-deposited samples moved about 40% toward the bottom of the potential energy landscape for amorphous materials. These results support the hypothesis that enhanced surface mobility allows stable glass formation by vapor deposition. A comparison of the enthalpy content of vapor-deposited glasses with aged glasses was used to evaluate the difference between bulk and surface dynamics for indomethacin; the dynamics in the top few nanometers of the glass are about 7 orders of magnitude faster than those in the bulk at Tg - 20 K.
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