Annealing of domain pattern of ferroelastic LaNbO₄ by computer simulation

To simulate the domain pattern of a large crystallite we propose to replace the atoms of crystal unit cell by another unit cell of the same size with one object, and to allow for simple phenomenological potential, which reproduces the lowest energy modes and the symmetry changes of the real crystal. This approach is applied to LaNbO ₄ crystal exhibiting a ferroelastic tetragonal - monoclinic phase transition. The crystal shows domain walls of type W′ oriented along directions specified by the potential parameters, and not by the mirror plane, as in many other ferroelastics. We have been able to simulate the annealing process on the sample of almost macroscopic size of 0.13×0.13×0.058 μm³ which, if not simplified, would contain almost 74 millions of atoms. In this way we could reproduce the typical domain patterns, and show their differences arising from thickness of the sample.