Surface reconstruction modes of Cu₂O(001) surface: A first principles study

The stabilization mechanism of the polar, copper terminated Cu₂O(001) surface by means of complex surface reconstruction was studied theoretically with a combination of static and molecular dynamics calculations. The experimentally reported "3√2 × 1" surface structure was constructed and characterized for the first time. The combination of simulated annealing with molecular dynamics shows that Cu⁺-Cu⁺ dimers are formed in the first layer along the equivalent [011] and [01-1] directions at elevated temperature. There is a relaxation of the atoms that separates copper cations from nearest neighbor rows. Using the experimentally observed superstructure cell allows decoupling the symmetry equivalent dimers. The structural reconstructions were characterized by the electronic properties calculations. It is observed that the dimers are formed due to the d-d interaction of the copper atoms. Finally, the symmetry driven reconstructed structure was investigated by DFT STM. The simulated STM images show that copper atoms have higher density than oxygen atoms at the surface and produce the positive surface corrugation.