ANNEALING OF DOMAIN PATTERN OF FERROELASTIC LANBO4 BY COMPUTER-SIMULATION

To simulate the domain pattern of a large crystallite we propose to re place the atoms of crystal unit cell by another unit cell of the same size with one object, and to allow for simple phenomenological potenti al, which reproduces the lowest energy modes and the symmetry changes of the real crystal. This approach is applied to LaNbO4 crystal exhibi ting a ferroelastic tetragonal - monoclinic phase transition. The crys tal shows domain walls of type W' oriented along directions specified by the potential parameters, and not by the mirror plane, as in many o ther ferroelastics. We have been able to simulate the annealing proces s on the sample of almost macroscopic size of 0.13x0.13x0.058 mu m(3) which, if not simplified, would contain almost 74 millions of atoms. I n this way we could reproduce the typical domain patterns, and show th eir differences arising from thickness of the sample.