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III.G.1.a.

Comparison of levels of theory for Si-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 1.8551
2
PM3 1.7948
3
PM6 1.8972
3
composite G2 1.9515
3
G3 1.9515
3
G3B3 1.9821
3
G4 1.9662
3
CBS-Q 1.9515
3

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(T+d)Z
hartree fock HF 1.9111
3
2.0579
3
1.9419
3
2.0641
3
1.9515
6
1.9515
3
1.9503
3
1.9485
3
1.9485
3
1.9482
3
1.9102
1
1.9577
3
1.9665
3
1.9530
3
1.9459
3
1.9695
3
1.9515
3
1.9449
3
1.9108
1
density functional LSDA 1.9411
3
1.9890
3
1.9612
3
2.0619
3
1.9736
3
1.9736
3
1.9708
3
1.9677
3
1.9677
3
1.9634
3
    1.9853
3
1.9655
3
1.9698
2
1.9824
3
1.9727
2
1.9115
1
 
SVWN   2.0519
3
    1.9359
2
  1.9708
3
                       
BLYP 1.9650
3
2.0862
3
1.9904
3
2.0968
3
2.0054
3
2.0054
3
2.0026
3
2.0016
3
2.0016
3
1.9949
3
    2.0157
3
1.9971
3
  1.9842
1
     
B1B95 1.9322
3
1.9818
3
1.9546
3
2.0565
3
1.9641
3
1.9650
3
1.9627
3
1.9618
3
1.9618
3
1.9596
3
    1.9782
3
1.9616
3
1.9684
2
1.9762
3
2.0244
1
1.9643
2
 
B3LYP 1.9447
3
2.0653
3
1.9691
3
2.0752
3
1.9821
3
1.9821
3
1.9799
3
1.9782
3
1.9938
2
1.9734
3
1.9384
1
1.9832
3
1.9934
3
1.9760
3
1.9687
3
1.9921
3
1.9729
3
1.9660
3
1.9380
1
B3LYPultrafine         1.9822
3
                      1.9658
3
   
B3PW91 1.9570
2
2.0573
3
1.9623
3
2.0646
3
1.9725
3
1.9725
3
1.9702
3
1.9686
3
1.9829
2
1.9653
3
    1.9850
3
1.9682
3
  1.9571
1
     
mPW1PW91 1.9522
2
2.0528
3
1.9711
2
2.0600
3
1.9675
3
1.9675
3
1.9654
3
1.9640
3
1.9640
3
1.9608
3
    1.9802
3
1.9640
3
  1.9528
1
     
M06-2X         1.9610
3
                           
PBEPBE 1.9716
2
2.0736
3
1.9925
2
2.0984
2
1.9912
3
1.9912
3
1.9885
3
1.9879
3
1.9879
3
1.9828
3
1.9516
1
  2.0027
3
1.9853
3
1.9913
2
  1.9579
1
1.9864
2
1.9509
1
PBEPBEultrafine         1.9645
1
                           
PBE1PBE         1.9678
3
                           
HSEh1PBE         1.9696
3
                           
TPSSh         1.9535
3
  1.9517
3
            1.9507
3
         
Moller Plesset perturbation MP2 1.9134
2
2.0610
3
1.9504
3
2.0685
3
1.9544
4
1.9601
3
1.9583
3
1.9567
3
1.9567
3
1.9620
3
  1.9672
3
1.9813
3
1.9586
4
1.9552
3
1.9870
3
1.9637
3
1.9839
2
1.9418
1
MP2=FULL 1.9129
2
2.0615
3
1.9571
2
2.0718
2
1.9526
4
1.9582
3
1.9563
3
1.9566
3
1.9654
2
1.9633
2
    1.9796
3
1.9581
3
1.9506
3
1.9713
1
  1.9556
2
1.9352
1
MP3         1.9562
3
  1.9424
3
                       
MP3=FULL         1.9414
3
  1.9393
3
                       
MP4   2.0884
2
    1.9785
3
    1.9573
1
1.9835
2
        1.9800
3
         
B2PLYP         1.9778
3
                1.9533
3
         
Configuration interaction CID   2.0793
2
1.9589
2
2.0864
2
1.9553
3
    1.9512
3
                     
CISD   2.0935
2
1.9649
2
2.1002
2
1.9613
3
    1.9719
2
                     
Quadratic configuration interaction QCISD   2.1038
3
1.9800
2
2.1312
2
1.9776
3
1.9930
2
1.9753
3
1.9724
3
1.9724
3
1.9904
2
    1.9996
3
1.9767
3
        1.9381
1
QCISD(T)         1.9843
3
    1.9495
1
        2.0242
2
1.9999
2
  2.0274
2
1.9979
2
   
Coupled Cluster CCD   2.0793
2
1.9619
2
2.0866
2
1.9588
3
1.9720
2
1.9692
2
1.9548
3
1.9689
2
1.9746
2
    1.9814
3
1.9776
2
  2.0004
2
1.9754
2
   
CCSD         1.9695
3
    1.9332
1
                     
CCSD(T)   2.0570
1
    1.9515
1
1.9515
1
1.9515
1
1.9458
1
1.9458
1
  1.9437
2
  2.0028
3
1.9814
3
  2.0076
3
1.9805
3
  1.9464
1
CCSD(T)=FULL 1.9165
1
      1.9769
3
1.9491
1
  1.9453
1
1.9453
1
      1.9697
1
1.9484
1
  1.9769
1
1.9459
1
   

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 2.0768
3
1.9655
3
2.0747
3
1.9638
3
2.0355
3
2.0589
3
density functional B1B95 2.0507
1
1.9655
1
       
B3LYP 2.0960
3
1.9978
3
2.0935
3
1.9971
3
2.0661
3
2.0702
3
Moller Plesset perturbation MP2 2.0778
3
1.9819
3
2.0797
3
1.9757
3
2.0504
3
2.0609
3
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.