(Equilibrium) Phase Diagram H2O Phase diagrams and phase transitions of unary systems Solids Phase transitions Phase transition temperature Kinetics vs thermodynamics Metastable phases Phase boundaries Boiling point Melting point Triple point Critical point Polymorphic forms Solid (Equilibrium) Phase Diagram H2O

1 bar Phase Diagram H2O

H-bonding 1 bar Tfus = Tcryst = 273.15 K Phase Diagram H2O

l g 1 bar Tvap = 373.15 K Phase Diagram H2O

1 bar 611 Pa 0.006 bar Triple point 273.16 K Phase Diagram H2O

Phase Diagram H2O Super critical sc Critical point 220.6 bar 1 bar Triple point 647.1 K Phase Diagram H2O

g g l l T Critical point

T < Tc(ritical) T > Tc H2O Critical point T Critical point 220.6 bar g g 647.1 K sc Super critical H2O l l T Critical point

Critical point 1 bar Triple point H-bonding Phase Diagram H2O

Polymorphic (solid state) phase transitions T < 40 ºC T > 40 ºC T > 60 ºC (Tfus = 70 ºC) Venlafaxine

Polymorphic forms characterized using X-Ray Powder Diffraction

Polymorphic phase transitions characterized using Differential Scanning Calorimetry

CO2 4He 1 bar 1 bar “dry ice” ambient conditions sublimation point at 1 bar “dry ice” CO2 4He

Phase transitions in phase diagrams of unary systems

(H2O)

(H2O) (H2O)

(H2O) 273.16 K 273.15 K 1 bar 0.006 bar (H2O) (H2O)

Clapeyron Clausius-Clapeyron

Ehrenfest classification of phase transitions Second order First order

Kinetic roughening transition for naphthalene crystals in a toluene solution

} C = 1 F = 2 P = 1 Gibbs phase rule F = C – P + 2 F: # degrees of freedom C: # components P: # phases

} C = 1 F = 1 P = 2 Gibbs phase rule F = C – P + 2

} C = 1 F = 0 P = 3 Gibbs phase rule F = C – P + 2

} C = 1 F = -1 P = 4 Gibbs phase rule F = C – P + 2