Dear RG members:
Screenshot from:
Vonsovskii, S. V. and Svirskii, M. S. 1961. About the spin of phonons. Soviet Physics of the Solid State. 3:2160. In Russian.
Do you know any article/book which uses explicit expressions containing Anisotropic Elastic Langragians L( Cij )?
For instance: cubic, hexagonal, or tetragonal ones? Other symmetries are also welcome.
L can be written in the 4th index range - ijkl or Voig - ij notations, but the math expressions must contain explicitly the elastic stiffness components Cij or compliances Sij (if S-1 C ~ 1) according to the point symmetry group.
For example: in the isotropy case: 2, in the cubic case 3, in the hexagonal case 6 and so on.
A lagrangian is defined as L(Cij) = K( ρ v2 ) - U( Cij ), therefore the potential term U(Cij) does have to include an expression invariant to the point group symmetry considered.
I did an intensive search on the web, so far only two papers with two expressions (isotropic and cubic cases) both papers from the '60s.
Thank you all so much for the interest.