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Amorphous polymorphism |
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| Authors: | Peter H. Poole Tor Grande F. Sciortino H. E. Stanley C. Austen Angell |
| Affiliation: | a Department of Chemistry, Arizona State University, Tempe, AZ 85287, USA b Department of Chemistry, Dalhousie University, Halifax, Nova Scotia B3H 4J3, Canada c Department of Inorganic Chemistry, Norwegian Institute of Technology, N-7034, Trondheim, Norway d Dipartimento di Fisica, Universita' “La Sapienza”, Piazzale Aldo Moro, 00185, Roma, Italy e Center for Polymer Studies and Physics Department, Boston University, Boston, MA 02215, USA |
| Abstract: | Recent studies of amorphous solid materials have revealed the possibility that more than one distinct amorphous phase may be formed from the same substance. In analogy with the phenomenon of crystalline polymorphism, this behavior has been termed “amorphous polymorphism”. We review the experimental manifestation of amorphous polymorphism, especially in tetrahedrally coordinated materials such as H2O and SiO2. Guided by computer simulation results on these substances we show how a thermodynamic explanation of these phenomena is possible, specifically that amorphous polymorphism occurs in substances where the thermodynamic behavior of the liquid state exhibits liquid-liquid phase separation, or a tendency toward it. We identify a number of systems which may also display amorphous polymorphism, and emphasize the central role to be played by computer simulation in the elucidation of this phenomenon. |
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