Frank elastic constants

Distortion free energy

Failed to parse (Conversion error. Server ("https://wikimedia.org/api/rest_") reported: "Cannot get mml. Server problem."): {\displaystyle F_{d}={\frac {1}{2}}K_{1}({\rm {div}}~\mathbf {n} )^{2}+{\frac {1}{2}}K_{2}(\mathbf {n} \cdot {\rm {curl}}~\mathbf {n} )^{2}+{\frac {1}{2}}K_{3}(\mathbf {n} \times {\rm {curl}}~\mathbf {n} )^{2}}