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

For BeCl2 (Beryllium chloride)

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) TZVP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ
Moller Plesset perturbation MP2=FULL -0.000671 -0.009846 -0.024871 -0.006601 -0.024959 -0.024959 -0.026316 -0.114129 -0.114129 -0.047199 -0.067666 -0.014040 -0.079781 -0.149256 -0.016670 -0.086925 -0.152162
MP3=FULL         -0.023245   -0.028453                    
MP4=FULL   -0.009233     -0.023712       -0.115511     -0.012715 -0.078523   -0.015347 -0.086322  
Coupled Cluster CCSD=FULL         -0.023148           -0.067019 -0.012247 -0.076763   -0.014772 -0.084464  
CCSD(T)=FULL         -0.023664           -0.067950 -0.012664 -0.078320   -0.015257 -0.086092  
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) TZVP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ