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

For SiH2+ (silicon dihydride cation)

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-pVTZ
Moller Plesset perturbation MP2=FULL -0.003001 -0.005514 -0.011914 -0.003558 -0.009592 -0.010106 -0.011242 -0.123409 -0.123843 -0.017512 -0.006125 -0.055548 -0.058991
MP3=FULL         -0.009554   -0.012151            
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-pVTZ