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

For C6H12 (2,3-dimethylbut-1-ene)

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 aug-cc-pVDZ aug-cc-pVTZ
Moller Plesset perturbation MP2=FULL -0.002788 -0.010095 -0.010095 -0.008228 -0.028939 -0.031068 -0.031571 -0.111769 -0.113441 -0.051733 -0.102584 -0.015878 -0.096220 -0.018286 -0.114691
MP3=FULL         -0.028632   -0.031274       -0.107484 -0.015004      
MP4=FULL   -0.009696     -0.028771       -0.118650     -0.014986      
B2PLYP=FULL -0.000845 -0.003024 -0.003024 -0.002459 -0.008561 -0.009171 -0.009321 -0.032007 -0.032508 -0.015032 -0.029419 -0.004735 -0.027901 -0.005448 -0.033142
Quadratic configuration interaction QCISD(T)=FULL         -0.028695             -0.014894      
Coupled Cluster CCSD=FULL         -0.028364           -0.107385 -0.014670      
CCSD(T)=FULL         -0.028705           -0.108083 -0.014895      
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 aug-cc-pVDZ aug-cc-pVTZ