Frank elastic constants

Distortion free energy

Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\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 }