J. Phys. IV France 05 (1995) C8-131-C8-136
Landau-Ginzburg Model of Interphase Boundaries in CsCl-Type Ferroelastics due to M-5 Mode Instability : LaAg1-xInxD.M. Hatch1, P. Hu1, A. Saxena2 and G.R. Barsch3
1 Department of Physics, Brigham Young University, Provo, Utah 84602, U.S.A.
2 Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, U.S.A.
3 Materials Research Laboratory and Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, U.S.A.
We have constructed a Landau-Ginzburg model of ferroelastic domain walls in the tetragonal phase of CsCl-type intermetallic compounds. This improper ferroelastic phase transition is driven by the condensation of a degenerate zone-edge phonon mode of M-5 symmetry and can be described by a six-component order parameter. Analytic and numerical kink-type soliton solutions for the order parameter profile and the strain distribution are obtained for three different interphase boundaries : a twin boundary and two antiphase boundaries. The stability, merging and splitting of various domain types are also studied. Specifically, a symmetry-allowed product phase of 14/mmm (D174h) symmetry has been experimentally observed in pseudobinary rare earth alloys of composition RAg1-x Inx (R=La, Ce, Pr) and in related systems (YCu, LaCd).
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