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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 C2+ atoms 1 and 2

For C2+ (carbon diatomic cation)
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 0.0002 0.0002 0.0002 0.0002 0.0020 0.0016 0.0016 0.0011 0.0010 0.0030 0.0009 0.0009 0.0055 0.0038 0.0011 0.0092 0.0039
MP3=FULL         0.0013   0.0012       0.0009 0.0013 0.0072        
MP4=FULL   0.0001     0.0017       0.0014     0.0011 0.0077   0.0013 0.0105  
B2PLYP=FULL 0.0001 0.0148 0.0000 0.0000 0.0031 0.0005 0.0031 0.0004 0.0004 0.0010 0.0003 0.0003 0.0020   0.0004 0.0028  
Quadratic configuration interaction QCISD(T)=FULL         0.0017             0.0011 0.0076   0.0013 0.0105  
Coupled Cluster CCSD=FULL         0.0016         0.0031 0.0011 0.0010 0.0074 0.0048 0.0012 0.0100 0.0049
CCSD(T)=FULL         0.0018           0.0010 0.0011 0.0075 0.0041 0.0013 0.0103 0.0042
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

c2q1.gif