Thermodynamics of surfaces and interfaces Atkins (ed. 10): §16C.2 Atkins (ed. 9): § Atkins (ed. 8): § Atkins (ed. 7): §
Na 2 ClO 3 crystals in solution solution
Large crystals grow; small crystals dissolve T = 0T = 1 day
Wilhelm Ostwald Large crystals grow; small crystals dissolve T = 0T = 1 day Ostwald ripening (1896)
Equilibrium: one single crystal T = 0T = 1 dayT = 10 daysT = 30 days
Equilibrium: one single crystal T = 0T = 1 dayT = 10 daysT = 30 days
Gibbs-Thomson effect -Interfacial (free) energy between two phases
Gibbs-Thomson effect -Interfacial (free) energy between two phases -Relevant for P >1 P =2,3 P =1
Laplace equation γ r γ r+dr equilibrium Laplace equation
Surface tension γ
Surface tension and capillary action Pressure of liquid column of height h Laplace equation equilibrium capillary action
Surface tension and capillary action
Surface tension and wetting
partial wetting partial dewetting Work (J/m 2 ) Force (N/m) }
Kelvin equation (nucleation barrier for condensation) γ l g P in P out Laplace equation Kelvin equation equilibrium constant T
nucleation barrier reason: interface energy between new phase and old classical nucleation theory –assume spherical nucleus, radius r –driving force: Δμ –surface free energy: γ –volume per growth unit: V 0 γ
nucleation barrier nucleation barrier and critical radius nucleation barrier depends on supersaturation (Δμ = σ) -low σ: no nucleation -high σ: easy nucleation
Polymorphism polymorphism: same chemical compound, different crystal structure (possible) differences in -melting point -solubility (bioavailability) -colour -morphology -etc. important for many industries, e.g. pharmaceuticals pseudo-polymorphism crystal structure containing the chemical compound, but including solvent (e.g. hydrate)
Polymorphism in Venlavaxine
Stability of polymorphic forms MonotropicEnantiotropic
Stable Polymorph Computer simulation Cluster Growth
Metastable Polymorph Computer simulation Cluster Growth
Stable polymorph Metastable polymorph
Computer simulation Cluster Growth