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Comparison of levels of theory for Si-N


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 1.5146
1
PM3 1.5644
2
PM6 1.5994
3
composite G2 1.6155
3
G3 1.6155
3
G3B3 1.6178
3
G4 1.5817
3
CBS-Q 1.6171
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 Def2TZVPP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(T+d)Z
hartree fock HF 1.8598
2
1.9767
3
1.8240
3
2.0836
3
1.6155
3
1.6155
3
1.6183
3
1.6128
3
1.6264
2
1.6013
3
1.5715
1
1.7544
3
1.5926
3
1.8729
3
1.6104
3
1.6162
2
1.8211
3
1.6249
2
1.6171
2
 
ROHF   1.5889
1
1.5438
1
  1.5400
1
1.5400
1
1.5425
1
1.5370
1
          1.5537
1
1.5403
1
         
density functional LSDA 1.6175
3
1.6362
3
1.6215
3
1.6766
3
1.6138
3
1.6138
3
1.6143
3
1.6092
3
1.6092
3
1.6035
3
      1.6263
3
1.6074
3
1.6205
2
1.6284
3
1.6273
2
1.6205
2
 
BLYP 1.6620
2
1.6894
3
1.6421
3
1.6994
3
1.6227
3
1.6349
3
1.6359
3
1.6311
3
1.6518
2
1.6440
2
      1.6468
3
1.6287
3
         
B1B95 1.6084
3
  1.6195
3
1.6786
3
1.6105
3
1.6111
3
1.6120
3
1.6077
3
1.6077
3
1.6027
3
      1.6247
3
1.6072
3
1.6214
2
1.5919
2
1.5833
1
1.6217
2
 
B3LYP 1.6426
2
1.6750
3
1.6256
3
1.6843
3
1.6178
3
1.6178
3
1.6191
3
1.6142
3
1.6345
2
1.6080
3
  1.6227
3
1.6007
3
1.6305
3
1.6129
3
1.6272
2
1.6336
3
1.6341
2
1.6276
2
 
B3LYPultrafine         1.6379
2
                        1.5855
2
   
B3PW91 1.6411
2
1.6748
3
1.6246
3
1.6827
3
1.6155
3
1.6155
3
1.6162
3
1.6118
3
1.6322
2
1.6066
3
      1.6288
3
1.6112
3
  1.5898
1
     
mPW1PW91 1.6371
2
1.6723
3
1.6430
2
1.7067
2
1.6122
3
1.6122
3
1.6130
3
1.6088
3
1.6290
2
1.6236
2
      1.6258
3
1.6084
3
         
M06-2X     1.6137
3
  1.6077
3
                             
PBEPBE 1.6574
2
1.7113
2
1.6613
2
1.7216
2
1.6512
2
1.6512
2
1.6513
2
1.6475
2
1.6475
2
1.6411
2
    1.6114
3
1.6648
2
1.6454
2
1.6396
2
    1.6398
2
 
PBE1PBE         1.6130
3
                             
HSEh1PBE   1.6738
3
    1.6138
3
  1.6146
3
              1.6098
3
         
TPSSh         1.6121
3
  1.6125
3
    1.6047
3
        1.6083
3
         
wB97X-D     1.6092
3
  1.6013
3
  1.6024
3
  1.5984
3
    1.6062
3
  1.6024
3
1.5984
3
    1.5994
3
   
B97D3   1.6668
3
    1.6189
3
  1.6192
3
  1.6162
3
  1.6085
3
      1.6144
3
    1.6256
3
   
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 Def2TZVPP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(T+d)Z
Moller Plesset perturbation MP2 1.6539
2
1.6705
3
1.6218
3
1.6773
3
1.6057
3
1.6138
3
1.6134
3
1.6002
3
1.6073
3
1.6052
3
  1.6155
3
1.5948
3
1.6261
3
1.6072
3
1.6006
3
1.6310
3
1.6096
3
1.6016
3
1.5274
1
MP2=FULL 1.6534
2
1.6707
3
1.6615
2
1.7220
2
1.6128
3
1.6128
3
1.6125
3
1.6066
3
1.6444
2
1.6393
2
      1.6254
3
1.6412
2
1.5944
3
1.5499
1
  1.6307
2
1.5235
1
MP3         1.6235
2
  1.5946
3
                         
MP3=FULL         1.5940
3
  1.5943
3
                         
MP4   1.7152
2
    1.6234
3
    1.5439
1
1.6545
2
          1.6203
3
         
B2PLYP         1.6237
3
                  1.6112
3
         
Configuration interaction CID   1.6822
2
1.6332
2
1.6995
2
1.5994
3
    1.5934
3
                       
CISD   1.7098
2
1.6411
2
1.7274
2
1.6090
3
    1.6262
2
                       
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 Def2TZVPP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(T+d)Z
Quadratic configuration interaction QCISD   1.7037
3
1.6570
2
1.7427
2
1.6265
3
1.6471
2
1.6274
3
1.6198
3
1.6198
3
1.6359
2
      1.6440
3
1.6193
3
        1.5720
1
QCISD(T)         1.6338
3
    1.5839
1
          1.6755
2
1.6495
2
  1.6829
2
1.6518
2
   
Coupled Cluster CCD   1.6860
2
1.6392
2
1.6958
2
1.6319
2
1.6319
2
1.6319
2
1.5963
3
1.6252
2
1.6231
2
      1.6449
2
1.6253
2
  1.6506
2
1.6275
2
   
CCSD         1.6449
2
                             
CCSD(T)           1.5864
1
  1.5795
1
          1.6726
2
1.6466
2
  1.6803
2
1.6491
2
   
CCSD(T)=FULL         1.6126
1
                             
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 Def2TZVPP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(T+d)Z

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         2.2467
2
1.6652
2
2.2440
2
1.8210
2
2.1775
2
2.2724
2
density functional B1B95         1.6298
1
1.5868
1
       
B3LYP         1.7108
2
1.6446
2
1.7109
2
1.6487
2
1.6796
2
1.6945
2
Moller Plesset perturbation MP2         1.7315
2
1.6528
2
1.7231
2
1.6553
2
1.6935
2
1.7044
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.