Surface energy of talc and chlorite: Comparison between electronegativity calculation and immersion results

The surface energies of talc and chlorite is computed using a simple model, which uses the calculation of the electrostatic energy of the crystal. It is necessary to calculate the atomic charges. We have chosen to follow Henry's model of determination of partial charges using scales of electronegativity and hardness. The results are in correct agreement with a determination of the surface energy obtained from an analysis of the heat of immersion data. Both results indicate that the surface energy of talc is lower than the surface energy of chlorite, in agreement with observed behavior of wettability. The influence of Al and Fe on this phenomenon is discussed. Surface energy of this type of solids seems to depend more strongly on the geometry of the crystal than on the type of atoms pointing out of the surface; i.e., the surface energy depends more on the physics of the system than on its chemistry. A calculation is performed in order to obtain the solid surface tension of ideal crystals of talc and chlorite. From this result, it is possible, using thermodynamic models, to calculate the heat of immersion in water of these solids and to compare with experimental data obtained for well-known samples. Results are in good agreement, confirming the differences between surfaces of talc and chlorite and confirming that a route of calculation of surface tension using electronegativity equalization is correct, even though it is very simple.