Symmetry Pattern and Domain Wall Structure in $GdFeO_{3}$ Perovskite Type

Symmetry relations between the domain states in $GdFeO_{3}$ type crystals have been obtained using group-theoretical analysis for prototype and ferroelastic space groups. Models for possible domain pairs are developed. The ion locations on the domain boundary were estimated as intermediate positions between the sites in crystal structure of neighboring domain states. It is shown that the crystalline structure of the boundary approaches to the prototype phase structure - the ideal $ABO_{3}$ perovskite-type structure, however certain deformations remain. In addition to the shifts of the all ions the tilts of oxygen octahedra of the some type and related displacements of A ions should take place during the switching of orientation states. The tilts of octahedra and displacements of A ions are sufficient to form translation states (antiphase domains). Antiphase domains can have boundaries between themselves basically along the three faces of the orthorhombic cell.