Regensburg 2010 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 60: Poster Session III (Methods: Atomic and electronic structure; Methods: electronic structure theory; Methods: Molecular simulations and statistical mechanics; Methods: Sanning probe techniques; Methods: other (experimental); Methods: other (theory) )
O 60.28: Poster
Mittwoch, 24. März 2010, 17:45–20:30, Poster B2
Analysis of XPD-patterns by means of Genetic Algorithms — •Tobias Lühr1, Daniel Weier1,2, Frank Schönbohm1,2, and Carsten Westphal1,2 — 1Fakultät Physik - TU Dortmund, Otto-Hahn-Str.4, D 44221 Dortmund, Germany — 2DELTA - TU Dortmund, Maria-Goeppert-Mayer-Str. 2, D 44227 Dortmund, Germany
Angle-scanned X-Ray Photoelectron Diffraction (XPD) is a powerful technique for the investigation of crystalline interfaces and surfaces. This technique provides the atomic structure of the investigated sample as well as the chemical state of the atoms. In order to determine the accurate structure from the recorded data it is necessary to simulate the XPD-pattern. A genetic algorithm was developed that generates and optimizes different surface structure models. Each structure is defined by a basic model structure and a transformation that depends on a reasonable size of variable parameters (genes). After generating a set of modified structures by variation of the genes the algorithm calculates the multiple scattering pattern for each structure and evaluates the pattern with an R-factor. If no R-factor has reached a specified value, the algorithm creates a new generation of parameter sets by a combination or mutation of the genes of the last generation. In this procedure the genes with a low R-factor are preferred to be chosen. With algorithm we present here it was possible to determine several atomic surface structures like Cyclopentene/Si(100), Pyridine/Si(100), and ZrSi2/Si(100).