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

For HNCNH2+ (diiminomethane, protonated)

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 -0.000896 -0.005246 -0.005246 -0.003699 -0.012412 -0.012923 -0.013305 -0.056646 -0.057183 -0.028190 -0.051866 -0.007513 -0.045424 -0.087766 -0.008627 -0.052888 -0.089573
MP3=FULL         -0.012158   -0.013003       -0.053882 -0.007051 -0.046556        
MP4=FULL   -0.004996     -0.011932       -0.059116     -0.006982 -0.046225   -0.008079 -0.054462  
B2PLYP=FULL -0.000269 -0.001559 -0.001559 -0.001100 -0.003634 -0.003795 -0.003912 -0.016131 -0.016283 -0.008053 -0.014789 -0.002218 -0.013063   -0.002546 -0.015234  
Quadratic configuration interaction QCISD(T)=FULL         -0.011920             -0.006950 -0.046242   -0.008041 -0.054446  
Coupled Cluster CCSD=FULL         -0.011896         -0.028540 -0.053771 -0.006877 -0.046229 -0.090780 -0.007956 -0.054222 -0.092426
CCSD(T)=FULL         -0.011935           -0.054068 -0.006955 -0.046305 -0.091518 -0.008046 -0.054476 -0.064398
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