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Comparison of levels of theory for I-I


Click on an entry for a histogram of the values.
The subscript refers to how many bonds of that type have been calculated.
average calculated bond lengths (Å)
Methods with predefined basis sets
semi-empirical AM1 2.5166
2
PM3 2.6591
2
PM6 2.3735
1

average calculated bond lengths (Å)
Methods with standard basis sets
STO-3G 3-21G 3-21G* 6-31G* 6-311G* Def2TZVPP
hartree fock HF 2.6528
1
2.8402
2
2.6445
2
  2.7028
1
2.6374
2
ROHF   2.7730
1
2.5926
1
     
density functional LSDA 2.7124
1
  2.6033
1
     
BLYP   2.9381
1
2.7497
1
  2.7747
1
 
B1B95 2.6943
1
  2.5990
1
  2.6939
1
 
B3LYP 2.7275
1
2.8702
2
2.6801
2
  2.7369
1
2.6629
2
B3LYPultrafine   2.8372
1
       
B3PW91 2.7135
1
2.8451
2
2.6534
2
  2.7060
1
 
mPW1PW91 2.7037
1
2.8350
2
2.6453
2
  2.6975
1
 
M06-2X 2.6926
1
2.7793
1
2.6358
2
     
PBEPBE 2.7378
1
2.8736
2
2.6714
2
  2.7265
1
2.6578
2
PBE1PBE 2.7004
1
  2.6047
1
     
HSEh1PBE 2.7034
1
2.8116
1
2.6116
1
     
TPSSh   2.8235
1
2.6187
1
     
wB97X-D     2.6499
2
     
B97D3   2.8822
2
       
STO-3G 3-21G 3-21G* 6-31G* 6-311G* Def2TZVPP
Moller Plesset perturbation MP2 2.7157
1
2.9076
2
2.6759
2
2.7361
1
2.7361
1
2.6302
2
MP2=FULL 2.7157
1
2.9085
2
2.6746
2
  2.7176
1
 
MP3         2.7306
1
 
MP4   2.9285
2
    2.7393
1
 
MP4=FULL   2.9095
1
       
B2PLYP 2.7208
1
2.8620
1
2.6392
1
     
B2PLYP=FULL 2.7208
1
2.8622
1
2.6388
1
     
Configuration interaction CID   2.9051
2
2.6711
2
  2.7120
1
 
CISD   2.9098
2
2.6721
2
  2.7129
1
 
STO-3G 3-21G 3-21G* 6-31G* 6-311G* Def2TZVPP
Quadratic configuration interaction QCISD   2.9234
2
2.6853
2
  2.7334
1
 
QCISD(T)         2.7438
1
 
Coupled Cluster CCD   2.9170
2
2.6833
2
  2.7304
1
 
CCSD(T)         2.7438
1
 
CCSD(T)=FULL         2.7463
1
 
STO-3G 3-21G 3-21G* 6-31G* 6-311G* Def2TZVPP

average calculated bond lengths (Å)
Methods with effective core potentials (select basis sets)
daug-cc-pVDZ daug-cc-pVTZ daug-cc-pVQZ Sadlej_pVTZ CEP-31G CEP-31G* CEP-121G CEP-121G* LANL2DZ SDD
hartree fock HF         2.7191
2
  2.7191
2
  2.7635
2
2.7546
2
density functional B3LYP         2.7826
2
  2.7826
2
  2.8227
2
2.8130
2
Moller Plesset perturbation MP2         2.8132
2
  2.8132
2
  2.8605
2
2.8486
2
For descriptions of the methods (AM1, HF, MP2, ...) and basis sets (3-21G, 3-21G*, 6-31G, ...) see the glossary in section I.C. Predefined means the basis set used is determined by the method.