Fig. 4. Net atomic charges of titanium atoms within the SrTiO₃(110) 4×1 training structures gathered from all three DFT-backed searches. The Ti charges are highlighted according to the depth parameter, with results for d = 3 Å in yellow, d = 6 Å in green and d = 9 Å in purple. z = 0 Å marks the SrTiO layer in the center of the surface slabs. The vertical lines indicate charges calculated for bulk systems with titanium in different oxidation states: TiO, Ti₂O₃, TiO₂ (rutile) and SrTiO₃.