Renormalization-group classification of continuous structural phase transitions induced by six-component order parameters.

The results of renormalization-group (RG) analysis in reciprocal space are reported for solid-solid phase transitions. We list the Landau-Ginzburg-Wilson Hamiltonian densities for six-component order parameters. The resulting RG recursion relations are derived by means of symmetric products of basic invariants. A list of fixed points for the densities is given and the stable fixed points are noted. Only two of the effective Hamiltonian densities possess stable fixed points. %'e indicate those specific structural transitions which are allowed to be continuous as determined by RG methods. We give critical exponents for the stable fixed points.