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Thermodynamics of surfaces and interfaces Atkins (ed. 10): §16C.2 Atkins (ed. 9): §17.8 + 17.10 Atkins (ed. 8): §18.7 + 18.8 Atkins (ed. 7): §6.8 - 6.10.

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Presentation on theme: "Thermodynamics of surfaces and interfaces Atkins (ed. 10): §16C.2 Atkins (ed. 9): §17.8 + 17.10 Atkins (ed. 8): §18.7 + 18.8 Atkins (ed. 7): §6.8 - 6.10."— Presentation transcript:

1 Thermodynamics of surfaces and interfaces Atkins (ed. 10): §16C.2 Atkins (ed. 9): §17.8 + 17.10 Atkins (ed. 8): §18.7 + 18.8 Atkins (ed. 7): §6.8 - 6.10

2 Na 2 ClO 3 crystals in solution solution

3 Large crystals grow; small crystals dissolve T = 0T = 1 day

4 Wilhelm Ostwald Large crystals grow; small crystals dissolve T = 0T = 1 day Ostwald ripening (1896)

5 Equilibrium: one single crystal T = 0T = 1 dayT = 10 daysT = 30 days

6 Equilibrium: one single crystal T = 0T = 1 dayT = 10 daysT = 30 days

7 Gibbs-Thomson effect -Interfacial (free) energy between two phases

8 Gibbs-Thomson effect -Interfacial (free) energy between two phases -Relevant for P >1 P =2,3 P =1

9 Laplace equation γ r γ r+dr equilibrium Laplace equation

10 Surface tension γ

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12 Surface tension and capillary action Pressure of liquid column of height h Laplace equation equilibrium capillary action

13 Surface tension and capillary action

14 Surface tension and wetting

15 partial wetting partial dewetting Work (J/m 2 ) Force (N/m) }

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17 Kelvin equation (nucleation barrier for condensation) γ l g P in P out Laplace equation Kelvin equation equilibrium constant T

18 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

19 nucleation barrier nucleation barrier and critical radius nucleation barrier depends on supersaturation (Δμ = σ) -low σ: no nucleation -high σ: easy nucleation

20 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)

21 Polymorphism in Venlavaxine

22 Stability of polymorphic forms MonotropicEnantiotropic

23 Stable Polymorph Computer simulation Cluster Growth

24 Metastable Polymorph Computer simulation Cluster Growth

25 Stable polymorph Metastable polymorph

26 Computer simulation Cluster Growth


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