Tensor representation of Oseen-Frank energy in uniaxial cholesterics.

DeGennes gave a 3-parameter representation of strain energy in a cholesteric liquid crystal that is second-order in a Q-tensor, and hence in order parameter. He left out a term involving an elastic constant, K24, which is relevant at surfaces and disclinations. The splay and bend elastic constants, K11 and K33, are alike in the second-order theory. The complete Oseen-Frank expression in terms of a director has 5 paramters, including K24.