A counterexample to the « maximal subgroup rule » for continuous crystalline transitions

Open Access
Publisher Website
Google Scholar
Abstract
We describe for the first time a theoretical example contradicting Ascher's conjecture of a maximal subgroup rule for the symmetry changes at continuous crystalline transitions. The example is that of a 4-dimensional order parameter spanning an irreducible representation of the space-group Go = I41. We show that this order parameter induces transitions towards groups G1 and G2, with G2 ⊂ G1 ⊂ G0 (G2 non maximal), on the basis of a Landau free-energy limited to fourth degree terms. By contrast, we have found no counterexample to the more precise conjecture by Michel stating that the maximal subgroup rule should hold with respect to the complete invariance group of the 4th degree Landau polynomial which is, in general, a supergroup of Go

This publication has 1 reference indexed in Scilit: