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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 NaK atoms 1 and 2

For NaK (Sodium Potassium)
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
Moller Plesset perturbation MP2=FULL 0.0156 0.0055 0.0290 0.0023 0.0273 0.0134 0.0140 0.0594 0.0296 0.0289 0.0311
MP3=FULL         -0.0147   0.0049        
Coupled Cluster CCSD(T)=FULL         0.0128           0.0190
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) TZVP

nakq1.gif