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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 He2+ atoms 1 and 2

For He2+ (helium 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
3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) 6-311+G(3df,2p) TZVP Def2TZVPP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ
Moller Plesset perturbation MP2=FULL 0.0000 0.0000 0.0000 0.0071 0.0000 0.0000 0.0359 0.0000 0.0000 0.0000 -0.0002 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
MP3=FULL       -0.0005   0.0000       0.0000 0.0000 0.0000 0.0000 0.0000        
MP4=FULL 0.0000     0.0000       0.0000   0.0000   0.0000 0.0000 0.0000   0.0000 0.0000  
B2PLYP=FULL -0.0355 0.0000 0.0000 -0.0154 0.0000 -0.0144 0.0000 -0.0004 0.0000 0.0000 0.0000 0.0000 0.0000 0.0361   0.0000 0.0000  
Quadratic configuration interaction QCISD(T)=FULL       0.0000           0.0000   0.0000 0.0000 0.0000   0.0000 0.0000  
Coupled Cluster CCSD=FULL       0.0000         0.0000 0.0000 0.0000 0.0000 0.0000 0.0000   0.0000 0.0000 0.0000
CCSD(T)=FULL       0.0000           0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000
3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) 6-311+G(3df,2p) TZVP Def2TZVPP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ

he2q1.gif