1. Unary and Binary Phase Diagrams
GLY 4200
Fall, 2012

2. Unary Diagrams Unary diagrams have a single component
We therefore usually choose to plot both P (pressure) and T (temperature) since composition is not a variable
Examples
Water
Silica
Carbon

3. Phase Rule for Unary Systems
f = c - p + 2 = 1- p + 2 = 3 - p
If one phase is present, there are two degrees of freedom (both T and P)
If two phases are present, there is one degree of freedom (either T or P)
If three phases are present, there are no degrees of freedom

4. H2O Diagram
Image: h2ophase.gif

5. Terminology
Image: triple_point.gif

6. Water ice
Image: ice-phase-diagram.gif

7. Silica Phase Diagram
Image: silica-phase-diag.gif

8. Snowflake Obsidian
The white patches are crystals of cristobolite, formed at high temperature
The magma-crystal mix then erupted, chilling the magma and forming a volcanic glass matrix around the metastable cristobolite, which cooled too quickly to revert to tridymite
Source:

9. Carbon Phase Diagram
Image: Carbon_Phase_Diagram.gif

10. Climate Change Application
From David Archer, Global Warming, figure 7.2
Greenhouse Warming on Terrestrial Planets