SKM 2023 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 40: Poster: Semiconductor Substrates

O 40.1: Poster

Dienstag, 28. März 2023, 18:00–20:00, P2/EG

Si(553)-Au and Si(775)-Au surface reconstructions with a genetic algorithm approach — •Leonard M. Verhoff and Simone Sanna — Instutute for theoretical physics, Giessen, Germany

It was found by simulations and experiments, that Au atoms on a Si(553)- and Si(755)-surface form metallic nanowires. However, their precise atomic structure is still under discussion.

In this work, the respective surface reconstructions with N adatoms are searched, using a genetic algorithm implemented in the program CALYPSO. Genetic algorithms are reported to be efficient methods for structure predictions.

In the first generation, all Au atoms are distributed randomly on the surface, meaning every adatom introduces 3 degrees of freedom. For each generated structure, the fitness, i.e. the configuration’s free energy, is then calculated from first principles with density functional theory implemented in VASP.

The next generation’s individuals are created by moving every structure in the 3N-dimensional space towards the structure that minimizes the fitness so far. To avoid getting stuck in a local energy minimum, 20% of the structured are created randomly in each generation.

The last step is repeated, until a certain convergence criterion is reached.