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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 AlH atoms 1 and 2

For AlH (aluminum monohydride)
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 6-31G* 6-31G** 6-31+G** 6-311G* cc-pVDZ cc-pVQZ aug-cc-pVDZ cc-pV(D+d)Z cc-pV(T+d)Z
Moller Plesset perturbation MP2=FULL -0.0000 0.0000 0.0006 0.0004 -0.0006 0.0007 0.0312 0.0040 0.0009 0.0020
MP3=FULL   0.0001   0.0009            
Coupled Cluster CCSD(T)=FULL                 0.0005 0.0021
3-21G 6-31G* 6-31G** 6-31+G** 6-311G* cc-pVDZ cc-pVQZ aug-cc-pVDZ cc-pV(D+d)Z cc-pV(T+d)Z

alhq1.gif