The situation with the MECI energy is instead slightly different. XMS has a stronger dependence on N state than XDW and RMS, and its decreasing trend is more pronounced than in the case of the excitation energies. The R-M-S deviation of RMS is instead only 0.024 eV, while that for XDW is also relatively small; this is because the zeroth-order description of S 0 and S 1 is a mixture of the two states for both, regardless of the value of N state .