2. Crystal forms

2.1 Free surface energy of a solid

By limiting ourselves to the consideration of single-component bodies, we can equate the surface tension γ with the free energy of the surface f ^(S) , that is, with the work expended to create a unit of new surface area. Like any free energy, f ^{(S )} contains a potential energy term (measured by the work expended to break intermolecular bonds) and an entropic term accounting for variations in the vibrational, translational, or rotational behavior of the molecules emerging at the surface, or in the number of configurations they can assume, all per unit area: $\gamma \approx f^{\left(S\right)}={\epsilon }_{}^{}$