Proper ferroelastic transitions in two dimensions: Anisotropic long-range kernels, domain wall orientations, and microstructure

For structural transitions with strain serving as the transition primary order parameter (proper ferroelastics), we obtain 23 proper ferroelastic transitions in two dimensions and derive distinct “elastic compatibility” kernels that specify anisotropic, long-range order-parameter interactions. These kernels influence possible domain-wall orientations, local rotations, and parent-product interfaces in two-dimensional ferroelastics. Using the approach described here, these results can be extended to two-dimensional improper ferroelastics and three-dimensional proper/improper ferroelastics.