Gibbs-Thomson effect
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The Gibbs-Thomson effect (not to be confused with the Thomson effect) relates surface curvature to vapor pressure and chemical potential. It is named after Josiah Willard Gibbs and three Thomsons: James Thomson, William Thomson, 1st Baron Kelvin, and Sir Joseph John Thomson.
It leads to the fact that small liquid droplets (i.e. particles with a high surface curvature) exhibit a higher effective vapor pressure, since the surface is larger in comparison to the volume. The Gibbs-Thomson effect can cause strong depression of the freezing point of liquids dispersed within fine porous materials.
Another notable example of the Gibbs-Thomson effect is Ostwald ripening, in which concentration gradients cause small precipitates to dissolve and larger ones to grow.
The Gibbs-Thomson equation for a precipitate with radius R is:
- VAtom : Atomic volume
- kB : Boltzmann constant
- γ : Surface tension (J
m− 2) - peq : Equilibrium partial pressure (or chemical potential or concentration)
- p : Partial pressure (or chemical potential or concentration)
- T : Absolute temperature
Ostwald ripening is thought to occur in the formation of orthoclase megacrysts in granites as a consequence of subsolidus growth. See rock microstructure for more.
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