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III.G.1.a.

Comparison of levels of theory for S-S


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 1.9206
10
PM3 1.9269
24
PM6 1.9767
27
composite G2 1.9560
28
G3 1.9560
28
G3B3 2.0223
28
G4 2.0136
29
CBS-Q 1.9099
19

average calculated bond lengths (Å)
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) 6-311+G(3df,2p) TZVP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(D+d)Z cc-pV(T+d)Z aug-cc-pV(T+d)Z cc-pCVDZ cc-pCVTZ Sadlej_pVTZ
hartree fock HF 2.0302
26
2.1925
28
1.9841
28
2.1516
28
2.0048
65
1.9934
28
1.9942
28
2.0004
28
2.0081
26
1.9911
26
1.9926
16
2.0054
28
2.0078
28
1.9877
28
1.8995
11
2.0070
28
1.9874
28
1.9167
8
1.9560
9
1.9768
21
1.9268
9
1.9431
4
1.9312
5
1.8992
1
ROHF   2.1712
5
1.9521
5
2.1666
3
1.9636
5
1.9637
5
1.9648
5
1.9705
5
2.0054
3
    2.0089
3
1.9755
5
1.9544
5
1.9815
1
2.0076
3
1.9861
3
1.9812
1
1.9481
3
1.9759
2
    1.9791
1
 
density functional LSDA 2.0477
28
2.1132
28
1.9917
28
2.1553
28
2.0064
28
2.0065
28
2.0056
28
2.0081
28
2.0084
28
1.9861
28
  2.0382
5
2.0145
28
1.9902
28
  2.0124
28
1.9773
8
2.0007
1
1.9670
6
1.9530
4
1.9520
4
  1.9524
1
 
SVWN   2.1786
28
    2.0157
25
2.0331
5
2.0053
28
2.0372
5
2.0380
5
2.0106
5
    2.0401
5
2.0159
5
  2.0387
5
2.0148
5
  1.9649
4
1.9264
5
1.9520
4
  1.9524
1
 
BLYP 2.0909
26
2.2409
28
2.0419
28
2.2113
28
2.0569
27
2.0571
27
2.0576
28
2.0643
28
2.0705
26
2.0149
17
  2.0967
5
2.0651
28
2.0410
28
  2.0882
14
    1.9907
7
1.9706
5
1.9691
5
  1.9995
1
 
B1B95 2.0490
26
2.1120
28
1.9883
28
2.1524
28
1.9994
28
2.0010
28
2.0005
28
2.0048
28
2.0109
26
1.9904
26
  2.0329
5
2.0097
28
1.9871
28
1.8988
4
2.0068
28
1.9645
13
1.8976
4
1.9452
7
1.9301
9
1.9296
9
1.9627
4
1.9396
5
 
B3LYP 2.0677
26
2.2095
28
2.0133
28
2.1797
28
2.0280
28
2.0281
28
2.0276
28
2.0327
28
2.0149
12
2.0134
25
2.0322
13
2.0334
28
2.0944
28
2.0136
28
1.9372
10
2.0344
28
1.9836
20
1.9387
8
1.9808
9
1.9990
23
1.9506
9
1.9867
4
1.9616
5
1.9415
1
B3LYPultrafine         2.0281
28
  1.9894
7
          2.0137
1
2.0312
16
  2.0144
1
2.0072
28
          1.9797
1
 
B3PW91 2.0673
20
2.1966
27
1.9982
28
2.1614
26
2.0111
28
2.0113
28
2.0107
28
2.0146
28
1.9970
12
1.9736
17
  2.0455
5
2.0200
28
1.9978
28
  2.0430
14
    1.9541
7
1.9356
5
1.9350
5
  1.9641
1
 
mPW1PW91 2.0610
20
2.1854
28
2.0014
24
2.1550
28
2.0066
28
2.0048
28
2.0043
28
2.0082
28
2.0143
26
1.9671
18
  2.0386
5
2.0135
28
1.9921
28
  2.0067
11
2.0178
5
  1.9493
7
1.9309
5
1.9304
5
  1.9597
1
 
M06-2X 2.0511
5
2.2075
5
2.0168
5
2.1789
5
2.0034
28
2.0306
5
2.0307
5
2.0362
5
2.0368
5
2.0136
5
  2.0507
3
2.0383
5
2.0171
5
  2.0369
5
2.0162
5
  1.8606
3
1.9326
5
1.9321
5
  1.9604
1
 
PBEPBE 2.0828
20
2.2823
20
1.9922
14
2.1594
14
2.0030
19
2.0032
19
2.0025
19
2.0066
19
2.0405
26
2.0155
26
2.0266
14
2.0641
5
2.0912
20
1.9883
19
1.9303
3
2.0246
8
2.0136
14
1.9283
3
1.9673
7
1.9542
9
1.9590
8
2.0088
3
1.9785
4
1.9220
1
PBEPBEultrafine         2.0335
25
              2.0079
1
1.9884
1
  2.0097
1
1.9885
1
          1.9767
1
 
PBE1PBE 2.0233
1
1.9692
1
1.9692
1
2.1440
1
1.9965
24
1.9837
1
1.9857
1
1.9890
1
1.9900
1
1.9650
1
  1.9906
1
1.9913
1
1.9697
1
  1.9918
1
1.9696
1
    2.0460
2
2.0462
2
  1.9585
1
 
HSEh1PBE 2.0594
5
2.2170
5
2.0188
5
2.1862
5
2.0114
26
2.0315
5
2.0319
5
2.0381
5
2.0391
5
2.0138
5
  2.0387
5
2.0401
5
2.0185
5
  2.0388
5
2.0177
5
  1.9089
4
1.9309
5
1.9304
5
  1.9596
1
 
TPSSh         1.9779
30
  1.9777
30
            1.9714
30
                   
Moller Plesset perturbation MP2 2.0737
20
2.2489
26
1.9928
28
2.2119
28
1.9969
31
2.0066
28
1.9960
42
2.0101
28
2.0149
26
1.9697
16
  2.0158
28
2.0250
28
1.9828
29
1.9247
6
2.0281
28
1.9889
14
1.9253
4
1.9712
9
1.9833
23
1.9489
7
1.9843
4
1.9513
5
1.9570
1
MP2=FULL 2.0733
20
2.2479
27
2.0006
24
2.2211
24
1.9954
31
2.0050
28
2.0048
28
1.9837
20
1.9933
12
1.9709
12
  2.0379
5
2.0212
27
1.9863
28
1.9230
4
1.9921
13
1.9906
8
1.8952
2
1.9689
9
1.9765
23
1.9395
7
1.9825
4
1.9471
5
 
ROMP2 2.0446
3
1.9839
3
1.9839
3
2.1730
3
1.9990
3
1.9993
3
1.9994
3
2.0051
3
2.0054
3
1.9829
3
  2.0099
3
2.0147
3
1.9869
3
  2.0178
3
            1.9511
1
 
MP3         2.0101
28
  1.9745
30
                      1.9585
3
1.8871
2
1.8851
2
  1.9695
1
 
MP3=FULL         1.9740
30
  1.9737
30
                                 
MP4 2.1214
8
2.2665
24
    2.0200
28
    2.0140
2
1.9936
10
    2.0099
1
2.0145
1
1.9853
13
  2.0196
1
1.9841
1
  1.9772
7
1.8762
3
1.8735
3
  1.9726
1
 
MP4=FULL   2.2169
1
    1.9963
1
      2.0042
1
      2.0129
1
1.9794
1
  2.0186
1
1.9763
1
          1.9690
1
 
B2PLYP         2.0128
23
                1.9528
23
                   
B2PLYP=FULLultrafine         2.0383
15
                                     
Configuration interaction CID 2.1038
8
2.2254
23
1.9686
15
2.1653
15
1.9988
28
2.0535
1
  1.9844
17
        2.0749
1
          1.8197
1
1.8054
1
1.8055
1
  1.9668
1
 
CISD 2.1039
8
2.2300
23
1.9648
14
2.1654
14
2.0550
28
2.0538
1
  1.9796
14
        2.0753
1
          1.8218
1
1.8075
1
1.8075
1
  1.9682
1
 
Quadratic configuration interaction QCISD 2.1214
10
2.2773
27
2.0107
24
2.2345
24
2.0710
28
2.0236
24
2.0126
27
2.0208
28
2.0104
16
2.0036
10
  2.0546
5
2.0073
19
1.9865
16
  2.0651
5
2.0301
5
  1.9802
9
1.9564
11
1.9460
5
  1.9799
1
 
QCISD(T)         2.0202
27
1.9591
2
1.9593
2
1.9882
4
2.0909
2
    2.0621
5
2.0189
10
1.9900
10
  2.0235
10
2.0005
8
  2.0090
3
1.9928
3
1.9930
3
  1.9824
1
 
Coupled Cluster CCD 2.1198
10
2.2532
24
2.0060
24
2.2183
24
2.0101
28
2.0193
24
2.0193
24
2.0223
26
2.0163
10
1.9991
10
  2.0473
5
2.0012
19
1.9878
12
  2.0167
8
1.9845
8
  1.9758
9
1.9404
10
1.9273
8
1.9425
2
1.9286
3
 
CCSD   2.1739
2
    1.9838
19
1.9386
2
1.9384
2
1.9713
4
2.0831
2
    2.0147
1
2.0289
7
1.9994
7
1.9730
1
2.0239
1
1.9888
1
1.9729
1
1.9995
3
2.0626
2
1.9824
3
  1.9776
1
 
CCSD=FULL         2.0000
1
            2.0142
1
2.0173
1
1.9848
1
1.9692
1
2.0230
1
1.9809
1
1.9686
1
        1.9731
1
 
CCSD(T)   2.1892
3
    2.0249
25
1.9647
6
1.9465
3
1.9865
4
2.0352
3
  1.9040
1
2.0606
5
2.0060
14
1.9748
16
1.9467
2
2.0101
14
1.9721
7
1.9765
1
2.0064
5
1.9734
7
1.9850
6
1.9945
4
1.9639
5
 
CCSD(T)=FULL         1.9982
12
            2.0600
5
2.0532
7
2.0207
7
1.9434
2
2.0602
7
2.0176
7
1.9725
1
1.9865
7
1.9491
9
1.9736
7
1.9921
4
1.9602
5
 

average calculated bond lengths (Å)
Methods with effective core potentials (select basis sets)
CEP-31G CEP-31G* CEP-121G CEP-121G* LANL2DZ SDD
hartree fock HF 2.1483
28
2.0075
28
2.1493
28
2.0061
28
2.1777
27
2.1796
27
density functional B1B95 2.1924
18
2.0465
18
2.2355
2
2.0865
2
2.2615
2
2.2448
2
B3LYP 2.1912
28
2.0441
28
2.1889
28
2.0412
28
2.2198
27
2.2055
28
Moller Plesset perturbation MP2 2.2122
28
2.0255
28
2.2112
28
2.0217
28
2.2375
27
2.2351
27
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.