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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 NCl+ atoms 1 and 2

For NCl+ (nitrogen monochloride 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) cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(T+d)Z
Moller Plesset perturbation MP2=FULL 0.0006 0.0019 0.0003 0.0018 0.1428 0.0008 0.0006 0.1487 0.0005 0.0019 0.0006 0.0020   0.0026   0.0023
MP3=FULL         -0.1396   -0.0468                  
Coupled Cluster CCSD(T)=FULL                         0.0030   0.0035  
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(T+d)Z

nclq1.gif