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Bond Length differences between FULL (all electrons correlated) and FROZEN core

Such as MP2=Frozen and MP2=Full
17 10 27 16 27

For BC atoms 1 and 2

For BC (boron monocarbide)
Bond length differences (full - frozen) in Å. Mouse over a difference for the bond length with full correlation.
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 0.0003 0.0001 0.0001 0.0001 0.0379 0.0008 0.0008 0.0354 0.0005 0.0020 0.0022 0.0004 0.0024 0.0019 0.0021 0.0159 0.0079
MP3=FULL         -0.0190   0.0001                    
MP4=FULL         0.0071               0.0199     0.0259  
Coupled Cluster CCSD=FULL         0.0024           0.0023 0.0015 0.0101 0.0069 0.0019 0.0149 0.0072
CCSD(T)=FULL         0.0112           0.0020 0.0016 0.0107 0.0070 0.0020 0.0158 0.0071
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

bcq1.gif