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. 2019 Jan 25;15(3):1492–1497. doi: 10.1021/acs.jctc.8b01277

Table 2. 3Eg and 5A1g Absolute Energies (au) and Spin Gap (kcal/mol) within the (40,38) Active Space for Various Truncation of the Many-Body Expansion in the CC Ansatz.

state CAS(40,38)/4B CCSD DCSD CCSD(T) CCSDT CCSDTQ
3Eg –1951.4360 –1951.4142 –1951.4281 –1951.4315 –1951.4357 –1951.4372
5A1g –1951.4290 –1951.4124 –1951.4232 –1951.4253 –1951.4286 –1951.4295
ΔE –4.4 –1.2 –3.1 –3.9 –4.4 –4.8
Δsp –1.3 –0.4 –0.5 –1.2 –1.3 –1.3