GLOBAL OPTIMIZATION IN LEED STRUCTURE DETERMINATION USING GENETIC ALGORITHMS

By application of search algorithms, low energy electron diffraction ( LEED) structure determination is now capable of solving relatively com plicated systems. However, since LEED is a diffraction technique, the danger remains in identifying an incorrect structure because a local r ather than a global minimum in the R-factor hypersurface was found. Re cently it has been suggested that simulated annealing could be employe d to circumvent this potential problem. In this Letter, using the Ir(1 10)-(1 x 2) missing row structure as an example, we demonstrate that g enetic algorithms can also be used for a full structural analysis. Our results indicate that a rough global search using a genetic algorithm , followed by structural refinement using conventional steepest descen t methods, should yield the correct structure within a typically tract able timescale.