Phase Diagrams

· Three cases exist for the enthalpy curves depending on bonding strength.

From: Brophy, et al.,
"Thermodynamics of
Structure," Wiley (1964)

· If A-atoms bond more strongly with B-atoms than with A-atoms, the enthalpy of the mixture is reduced (negative deviation).
· If bonding between A- and B-atoms is essentially the same as the bonding between A-A or B-B, the enthalpy varies linearly with composition (ideal).
· If like-atoms bond more strongly than unlike-atoms, the enthalpy of the mixture is increased above the linear ideal case (positive deviation).