Superficial and molecular energies

Where n0 is the number of molecules contained per square meter of layer, the relationship between the energy per surface unit Es and the energy per molecule Em is:

This relationship applies to Ecou and Eflx. However, crystallization energy typically concerns the molecule. However, where N0 is the number of molecules per volume unit, we have:

where Evcris is the crystallization energy per volume unit.

Surface energy

The interfacial crystal-solution energy depends on:

  • - temperature;
  • - the characteristics of the solution and of the crystal.

According to Onsager [ONS 44], the linear energy of the edge of a face is as follows:

where J and J' are the interaction energies in two perpendicular directions. This energy is cancelled for:

When this temperature is reached, the crystal growth becomes rough. This is thermal transition.

The surface energy is: a: dimension of one molecule (m)

For conditions close to ambience, Mersmann proposed the following correlation for surface energy:

ps: real density of crystal (kg.m-3)

M: molar mass (kg.kmol-1)

Na: Avogadro number (6.02.1026 molecules.kmol-1) cL : molar concentration of the saturation liquor

< Prev   CONTENTS   Source   Next >