Ab Initio Predictions of Double-Layer TiO2-Terminated SrTiO3(001) Surface Reconstructions

Predicting oxide surface structures, and surface structures in general, is a significant science frontier. Herein, we demonstrate an Ising model approach combined with density-functional calculations to predict several SrTiO3(001) surface reconstructions. Constrained Ising tilings of TiO5 square truncated octahedral units are used to construct the TiO2 adlayers of SrTiO3(001) surface reconstructions with TiO2 double-layer terminations for a given periodicity and composition. This method is used to re-examine the (root 5 x root 5)R26.6 degrees reconstruction and to predict several (root 10 x root 10)R18.4 degrees reconstructions. The surface structures and energies of the newly predicted reconstructions, along with consideration of the previously reported (root 13 x root 13)R33.7 degrees, 3 x 3, and (root 2 x root 2)R45.0 degrees reconstructions, indicate that the larger, more complex TiO2 double-layer SrTiO3(001) reconstructions with lower coverages of the TiO2 adlayer are made up of recurrent structural motifs represented by smaller, simpler reconstructions with higher coverages of the TiO2 adlayer. These results demonstrate a route forward for predicting oxide and other surface structures using a relatively simple computational approach.