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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 SiH+ atoms 1 and 2

For SiH+ (silicon monohydride 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 0.0001 -0.0001 -0.0000 0.0000 -0.0017 0.0006 0.0006 -0.0017 0.0005 0.0016 0.0007 0.0005 0.0024 0.0120 0.0036 0.0048 0.0152
MP3=FULL         0.0004   0.0019       0.0007 0.0007 0.0023        
MP4=FULL   0.0000     0.0000       0.0002     0.0006 0.0023   0.0038 0.0049  
B2PLYP=FULL 0.0000 -0.0001 -0.0000 0.0000 -0.0015 0.0002 -0.0010 -0.0002 -0.0004 0.0007 0.0002 0.0002 0.0010   0.0010 0.0015  
Quadratic configuration interaction QCISD(T)=FULL         0.0001             0.0010 0.0023   0.0036 0.0049  
Coupled Cluster CCSD=FULL         0.0004         0.0023 0.0008 0.0013 0.0018 0.0114 0.0040 0.0044 0.0143
CCSD(T)=FULL         -0.0000           0.0007 0.0009 0.0023 0.0114 0.0035 0.0049 0.0144
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

sihq1.gif