Frank elastic constants

Distortion free energy

$F_{d}={\frac {1}{2}}K_{1}({\rm {div}}~\mathbf {n} )^{2}+{\frac {1}{2}}K_{2}(\mathbf {n} \cdot {\rm {curl}}~\mathbf {n} )^{2}+{\frac {1}{2}}K_{3}(\mathbf {n} \times {\rm {curl}}~\mathbf {n} )^{2}$

References

1. F. C. Frank "I. Liquid crystals. On the theory of liquid crystals", Discussions of the Faraday Society 25 pp. 19-28 (1958)
2. Michael P. Allen and Daan Frenkel "Calculation of liquid-crystal Frank constants by computer simulation", Physical Review A 37 1813-1816 (1988)