Fang et al. (2014) compiled a subset of 96 excitations of 79 different organic and inorganic molecules, including basic PP. They have assessed diverse DFT functionals (BP86, B3LYP, PBE0, M06-2X, M06-HF, CAM-B3LYP and ωB97XD) and two wave-function based approaches (CIS and CC2). Overall, the lowest error was produced by CC2 with MAE of 0.19 eV. However, it was found that CC2 approach did not perform well for inorganic systems (MAE: 0.31 eV) while the MAE of B3LYP is only 0.22 eV.