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Energy differences between frozen core and all electrons correlated.
MP2, MP3, MP4, B2PLYP, CCSD, and CCSD(T)

For C5H7 (cyclopentenyl radical)

Energies in Hartree
Methods with standard basis sets
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) cc-pVDZ cc-pVTZ aug-cc-pVDZ aug-cc-pVTZ
Moller Plesset perturbation MP2=FULL -0.002206 -0.008298 -0.008298 -0.006675 -0.019273 -0.025377 -0.025796 -0.088301 -0.094272 -0.041089 -0.012626 -0.078191 -0.014652 -0.098237
MP3=FULL         -0.028881   -0.034797              
Coupled Cluster CCSD(T)=FULL         2.665981           -0.011799 -0.056277 -0.013785 -0.096534
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) cc-pVDZ cc-pVTZ aug-cc-pVDZ aug-cc-pVTZ