STABLE BINARY PLANAR STRUCTURES FROM MONTE-CARLO SIMULATION

摘要

From a two dimensional random mixture of NA atoms A and Nb atoms B with convenient distance ratios, a Monte-Carlo simulation with Lennard-Jones interactions characterized by the energy parameters EM,EAS,￡I1B enables us to derive their optimal structures at a given temperature and concentration. Slow annealing and cooling processes are used in order to obtain low temperature stable structures. Depending on the parameters, some segregation effects or homogeneous phases are observed. Numerous local and medium range orders are noted and compared with those observed in arrangements of Robinson triangles and Robinson tilings in order lo classify these structures. There is clear evidence of facetting of the boundary of these clusters in most of the low temperature structures. Temperature effects are also studied and show a gradual transition from low temperature order to higher temperature mixing and disorder. Diffraction patterns of the structures are deduced and linked with the observations of medium range order.