  Using molecular dynamics simulation with an angle-dependent Lennard-Jones
potential, we study orientational glass with quadrupolar symmetry in mixtures
of elliptic particles and circular impurities in two dimensions. With a mild
aspect ratio ($=1.2$) and a mild size ratio ($=1.2$), we realize a plastic
crystal at relatively high temperature $T$. With further lowering $T$, we find
a structural phase transition for very small impurity concentration $c$ and
pinned disordered orientations for not small $c$. The ellipses are anchored by
the impurities in the planar alignment. With increasing $c$, the orientation
domains composed of isosceles triangles gradually become smaller, resulting in
orientational glass with crystal order. In our simulation, the impurity
distribution becomes heterogeneous during quenching from liquid, which then
produces rotational dynamic heterogeneities. We also examine rheology in
orientational glass to predict a shape memory effect and a superelasticity
effect, where a large fraction of the strain is due to collective orientation
changes.

Soft Condensed Matter;Materials Science;Statistical Mechanics