so a negative error implies xTB-sTDA is over-predicting the excited state energy. As seen in Figure (a), there are distinct regions where xTB-sTDA over-predicts S 1 (right side), regions where xTB-sTDA has reasonable accuracy (top left and center), and regions where it under-predicts (bottom left and top). In general, most molecules are within ±0.5eV error.