Table 3. Energy Difference ΔE = E(3ax) – E(3eq) and Spin-State Splittings ΔE = ES(3) – ET(3) in kJ/mola.
| state | func | spin | ΔEQM/MM | ΔEQM+ptch | ΔEQM | ΔEMM | ΔEbig-QM |
|---|---|---|---|---|---|---|---|
| 3fix | TPSS-D3 | S = 1 | 63.4 | 76.5 | 74.9 | –4.4 | |
| 3free | TPSS-D3 | S = 1 | 67.8 | 51.0 | 65.5 | –14.6 | 87.7 |
| 3axfree | TPSS-D3 | S = 1,0 | 4.2 | 5.4 | 2.7 | –1.2 | |
| 3axfree | B3LYP-D3 | S = 1,0 | –0.7 | 0.8 | 2.8 | –1.2 | |
| 3eqfree | TPSS-D3 | S = 1,0 | 12.5 | 10.6 | 14.0 | 2.0 | 10.5 |
| 3eqfree | B3LYP-D3 | S = 1,0 | 13.2 | 11.2 | 16.5 | 2.0 |
a
ΔEQM/MM and ΔEQM+ptch are defined in eq 1 and ΔEQM/MM = EMM123 – EMM1 from the same equation. EQM is the energy of the QM system, without any point-charge model. Ebig-QM is the big-QM energy. All energies were calculated or extrapolated (ΔEbig-QM) with the def2-TZVPP basis set on structures optimized using QM/MM using the def2-SV(P) basis set. In ΔEbig-QM, 10.8 kJ/mol (3free) or −1.3 kJ/mol (3eqfree) of the total energy is a correction obtained as the difference between def2-TZVPP and def2-SV(P) calculations on the QM systems in Figure 6.