FITTING DOZENS OF COORDINATES BY LEED - AUTOMATED-DETERMINATION OF COMPLEX SURFACE-STRUCTURES

We present the first comprehensive discussion of automatic optimizatio n procedures for surface-structure determination by LEED. These proced ures combine numerical search algorithms with efficient methods of det ermining the diffracted intensities for varying structures. Such appro aches can reduce the computer time required for an entire structure de termination by many orders of magnitude, while fitting many times more unknown structural parameters. Thereby, relatively complex structures , with typically 10 adjustable atoms (or 30 adjustable coordinates), c an be readily determined on today's workstations. We list over two doz en structures so determined, many as yet unpublished.