Difference between revisions of "Polyamorphic systems"

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Some solid compounds can exist in two or more '''polymorphs''' with different atomic structures but the same chemical composition.
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'''Polyamorphic systems''' and liquid-liquid transitions. Some solid compounds can exist in two or more ''polymorphs'' with different atomic structures but the same chemical composition.
In the case of a pure element, this behavior is termed '''allotropy'''.
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In the case of a pure element, this behavior is termed ''allotropy''.
The existence of liquid polymorphs is known as '''polyamorphism''', i.e. the ability of a substance to exist in several different amorphous modifications.  
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The existence of liquid polymorphs is known as ''polyamorphism'', i.e. the ability of a substance to exist in several different amorphous modifications.  
 
Note: glasses are not in thermodynamic equilibrium, so such transformations do not correspond to true phase transitions from one stable liquid to another.
 
Note: glasses are not in thermodynamic equilibrium, so such transformations do not correspond to true phase transitions from one stable liquid to another.
 
===Polyamorphic systems===
 
===Polyamorphic systems===

Revision as of 16:07, 22 February 2008

Polyamorphic systems and liquid-liquid transitions. Some solid compounds can exist in two or more polymorphs with different atomic structures but the same chemical composition. In the case of a pure element, this behavior is termed allotropy. The existence of liquid polymorphs is known as polyamorphism, i.e. the ability of a substance to exist in several different amorphous modifications. Note: glasses are not in thermodynamic equilibrium, so such transformations do not correspond to true phase transitions from one stable liquid to another.

Polyamorphic systems

Real systems that present liquid-liquid transitions:

Models

Idealised models that present liquid-liquid transitions:

General reading

  1. C. A. Angell "Formation of Glasses from Liquids and Biopolymers", Science 267 pp. 1924 - 1935 (1995)
  2. Peter H. Poole, Tor Grande, C. Austen Angell, Paul F. McMillan "Polymorphic Phase Transitions in Liquids and Glasses", Science 275 pp. 322 - 323 (1997)
  3. Paul McMillan "Phase transitions: Jumping between liquid states", Nature 403 pp. 151-152 (2000)
  4. Jeff L. Yarger and George H. Wolf "Polymorphism in Liquids", Science 306 pp. 820 - 821 (2004)