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Comparison of levels of theory for Si-Se


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 PM3 1.9340
2
PM6 1.9783
2
composite G2 2.0214
2
G3 2.0418
2
G3B3 2.0766
2
G4 2.0708
2
CBS-Q 2.0221
2

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 daug-cc-pVDZ daug-cc-pVTZ
hartree fock HF 2.0244
2
2.1220
2
2.0265
2
2.0986
2
2.0214
2
2.0214
2
2.0335
2
2.0395
2
2.0395
2
2.0195
2
2.0410
2
2.0477
2
2.0532
2
2.0472
2
2.0425
2
2.0587
2
2.0473
2
2.0426
2
2.0453
1
2.0587
2
2.0472
2
ROHF   2.1270
1
2.0056
1
2.1000
1
1.9980
1
1.9980
1
2.0088
1
2.0158
1
2.0158
1
  2.0158
1
2.0231
1
2.0306
1
2.0229
1
2.0175
1
2.0337
1
2.0225
1
2.0175
1
2.0453
1
2.0337
1
2.0223
1
density functional LSDA                                     2.0622
1
   
BLYP 2.0697
2
2.1637
2
2.0775
2
2.1435
2
2.0796
2
2.0796
2
2.0923
2
2.0956
2
2.0956
2
2.0667
2
2.0881
2
2.0985
2
2.1059
2
2.0932
2
  2.1072
2
2.0928
2
  2.0978
1
2.1070
2
2.0928
2
B1B95 2.1254
2
2.0375
2
2.0375
2
2.1016
2
2.0343
2
2.0343
2
2.0455
2
2.0509
2
2.0509
2
2.0279
2
2.0477
2
2.0558
2
2.0619
2
2.0526
2
  2.0638
2
2.0524
2
  2.0574
1
2.0725
1
2.0524
2
B3LYP 2.1393
2
2.1410
2
2.0555
2
2.1222
2
2.0553
2
2.0553
2
2.0673
2
2.0708
2
2.0708
2
2.0449
2
2.0650
2
2.0747
2
2.0818
2
2.0704
2
2.0658
2
2.0836
2
2.0701
2
2.0657
2
2.0742
1
2.0835
2
2.0700
2
B3LYPultrafine   2.1410
2
    2.0553
2
2.0553
2
2.0673
2
2.0708
2
  2.0449
2
2.0650
2
2.0747
2
2.0818
2
2.0704
2
  2.0836
2
2.0701
2
  2.0742
1
2.0835
2
2.0700
2
B3PW91 2.1346
2
2.1318
2
2.0471
2
2.1107
2
2.0439
2
2.0439
2
2.0551
2
2.0596
2
2.0596
2
2.0354
2
2.0554
2
2.0642
2
2.0706
2
2.0602
2
  2.0727
2
2.0601
2
  2.0662
1
2.0727
2
2.0601
2
mPW1PW91 2.1299
2
2.1273
2
2.0426
2
2.1063
2
2.0391
2
2.0391
2
2.0499
2
2.0546
2
2.0546
2
2.0311
2
2.0509
2
2.0593
2
2.0655
2
2.0558
2
  2.0678
2
2.0557
2
  2.0617
1
2.0679
2
2.0557
2
M06-2X 2.1180
2
2.1257
2
2.0414
2
2.1052
2
2.0373
2
2.0373
2
2.0484
2
2.0549
2
2.0549
2
2.0323
2
2.0542
2
2.0616
2
2.0667
2
2.0605
2
  2.0692
2
2.0601
2
  2.0607
1
2.0693
2
2.0600
2
PBEPBE 2.0592
2
2.1498
2
2.0652
2
2.1276
2
2.0631
2
2.0631
2
2.0748
2
2.0796
2
2.0796
2
2.0527
2
2.0739
2
2.0834
2
2.0895
2
2.0787
2
  2.0912
2
2.0786
2
  2.0861
1
2.0912
2
2.0786
2
PBEPBEultrafine   2.1498
2
    2.0631
2
2.0631
2
2.0748
2
2.0796
2
  2.0527
2
2.0739
2
2.0834
2
2.0895
2
2.0787
2
  2.0912
2
2.0786
2
  2.0861
1
2.0912
2
2.0786
2
PBE1PBE 2.1288
2
2.0432
2
2.0432
2
2.1069
2
2.0393
2
2.0393
2
2.0501
2
2.0551
2
2.0551
2
2.0315
2
2.0514
2
2.0599
2
2.0658
2
2.0564
2
  2.0681
2
2.0563
2
  2.0624
1
2.0681
2
2.0563
2
HSEh1PBE 2.1303
2
2.1300
2
2.0449
2
2.1095
2
2.0412
2
2.0412
2
2.0524
2
2.0572
2
2.0572
2
2.0332
2
2.0532
2
2.0623
2
2.0681
2
2.0584
2
  2.0704
2
2.0583
2
  2.0646
1
2.0704
2
2.0582
2
TPSSh 2.1375
2
2.1372
2
2.0501
2
2.1126
2
2.0448
2
2.0448
2
2.0560
2
2.0616
2
2.0616
2
2.0361
2
2.0568
2
2.0660
2
2.0723
2
2.0612
2
2.0577
2
2.0744
2
2.0614
2
2.0576
2
2.0691
1
2.0744
2
2.0614
2
wB97X-D 2.1182
2
2.1153
2
2.0345
2
2.0966
2
2.0306
2
2.0306
2
2.0415
2
2.0455
2
2.0455
2
2.0246
2
2.0430
2
2.0507
2
2.0571
2
2.0484
2
2.0445
2
2.0599
2
2.0482
2
2.0444
2
2.0515
1
2.0598
2
2.0482
2
B97D3 2.0686
2
2.1545
2
2.0664
2
2.1311
2
2.0648
2
2.0648
2
2.0771
2
2.0824
2
2.0824
2
2.0534
2
2.0754
2
2.0859
2
2.0924
2
2.0799
2
2.0755
2
2.0941
2
2.0795
2
2.0754
2
2.0864
1
2.0940
2
2.0795
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 cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(T+d)Z daug-cc-pVDZ daug-cc-pVTZ
Moller Plesset perturbation MP2 2.0368
2
2.1531
2
2.0465
2
2.1370
2
2.0463
2
2.0463
2
2.0550
2
2.0564
2
2.0564
2
2.0346
2
2.0509
2
2.0559
2
2.0645
2
2.0495
2
2.0406
2
2.0674
2
2.0498
2
2.0398
2
2.0705
1
2.0671
2
2.0493
2
MP2=FULL 2.0369
2
2.1536
2
2.0449
2
2.1358
2
2.0428
2
2.0428
2
2.0515
2
2.0539
2
2.0539
2
2.0219
2
2.0450
2
2.0578
2
2.0626
2
2.0450
2
2.0380
2
2.0654
2
2.0416
2
2.0361
2
2.0635
1
2.0650
2
2.0413
2
ROMP2 2.0270
1
2.0523
1
2.0523
1
2.1065
1
2.0524
1
2.0524
1
2.0618
1
2.0635
1
2.0635
1
2.0448
1
2.0615
1
2.0650
1
2.0731
1
2.0598
1
  2.0775
1
    2.0708
1
2.0777
1
2.0595
1
MP3         2.0415
2
  2.0506
2
      2.0483
2
2.0536
2
2.0625
2
2.0481
2
        2.0590
1
2.0661
2
2.0477
2
MP3=FULL   2.1457
2
2.0399
2
2.1305
2
2.0384
2
2.0384
2
2.0475
2
2.0509
2
2.0509
2
2.0209
2
2.0450
2
2.0561
2
2.0609
2
2.0447
2
  2.0647
2
2.0411
2
  2.0541
1
2.0642
2
2.0409
2
MP4   2.2003
2
    2.0646
2
      2.0747
2
  2.0685
2
2.0760
2
2.0859
2
2.0681
2
  2.0871
2
2.0678
2
  2.0876
1
2.0867
2
2.0677
2
MP4=FULL   2.2014
2
    2.0610
2
      2.0732
2
  2.0636
2
  2.0840
2
2.0638
2
  2.0851
2
2.0598
2
  2.0816
1
2.0845
2
2.0596
2
B2PLYP 2.1430
2
2.1540
2
2.0572
2
2.1310
2
2.0570
2
2.0570
2
2.0688
2
2.0720
2
2.0720
2
2.0462
2
2.0665
2
2.0751
2
2.0827
2
2.0695
2
  2.0860
2
2.0695
2
  2.0762
1
2.0860
2
2.0694
2
B2PLYP=FULL 2.1429
2
2.1541
2
2.0566
2
2.1307
2
2.0554
2
2.0554
2
2.0672
2
2.0710
2
2.0710
2
2.0414
2
2.0641
2
2.0758
2
2.0820
2
2.0678
2
  2.0852
2
2.0666
2
  2.0734
1
2.0851
2
2.0665
2
B2PLYP=FULLultrafine 2.1429
2
2.1541
2
2.0566
2
2.1307
2
2.0554
2
2.0554
2
2.0672
2
2.0710
2
2.0710
2
2.0414
2
2.0641
2
2.0758
2
2.0820
2
2.0678
2
  2.0852
2
2.0666
2
  2.0734
1
2.0851
2
2.0665
2
Configuration interaction CID   2.1419
2
2.0382
2
2.1252
2
2.0381
2
    2.0491
2
    2.0443
2
  2.0602
2
2.0437
2
        2.0512
1
2.0630
2
2.0428
2
CISD   2.1495
2
2.0433
2
2.1286
2
2.0438
2
    2.0550
2
    2.0494
2
  2.0668
2
2.0475
2
        2.0538
1
2.0692
2
2.0464
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 cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(T+d)Z daug-cc-pVDZ daug-cc-pVTZ
Quadratic configuration interaction QCISD   2.1793
2
2.0621
2
2.1526
2
2.0632
2
2.0632
2
2.0751
2
2.0765
2
2.0765
2
2.0504
2
2.0698
2
2.0799
2
2.0910
2
2.0685
2
  2.0951
2
2.0680
2
  2.0697
1
2.0951
2
2.0675
2
QCISD(T)         2.0713
2
    2.0856
2
    2.0795
2
2.0895
2
2.0997
2
2.0787
2
  2.1046
2
2.0784
2
  2.0812
1
2.1046
2
2.0780
2
QCISD(T)=FULL         2.0662
2
  2.0785
2
      2.0728
2
  2.0971
2
2.0731
2
2.0629
2
2.1019
2
2.0686
2
2.0604
2
2.0742
1
2.1017
2
2.0684
2
QCISD(TQ)         2.0616
2
  2.0733
2
      2.0731
2
  2.0893
2
2.0723
2
2.0613
2
2.0956
2
2.0726
2
2.0667
1
  2.0957
2
2.0723
2
QCISD(TQ)=FULL         2.0570
2
  2.0685
2
          2.0869
2
2.0726
1
  2.0930
2
      2.0984
1
 
Coupled Cluster CCD   2.1469
2
2.0432
2
2.1319
2
2.0435
2
2.0435
2
2.0527
2
2.0541
2
2.0541
2
2.0333
2
2.0499
2
2.0560
2
2.0651
2
2.0497
2
  2.0686
2
2.0494
2
  2.0587
1
2.0683
2
2.0490
2
CCSD         2.0539
2
2.0539
2
2.0651
2
2.0668
2
2.0668
2
2.0437
2
2.0624
2
2.0703
2
2.0803
2
2.0618
2
2.0505
2
2.0853
2
2.0615
2
2.0495
2
2.0638
1
2.0854
2
2.0611
2
CCSD=FULL         2.0495
2
        2.0299
2
2.0561
2
2.0723
2
2.0781
2
2.0569
2
2.0474
2
2.0830
2
2.0524
2
2.0452
2
2.0578
1
2.0828
2
2.0522
2
CCSD(T)         2.0649
2
2.0649
2
2.0763
2
2.0779
2
2.0779
2
2.0540
2
2.0733
2
2.0814
2
2.0916
2
2.0727
2
2.0612
2
2.0963
2
2.0724
2
2.0602
2
2.0777
1
2.0962
2
2.0720
2
CCSD(T)=FULL         2.0603
2
          2.0671
2
2.0833
2
2.0892
2
2.0676
2
2.0582
2
2.0938
2
2.0636
2
2.0556
2
2.0713
1
2.0935
2
2.0634
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 cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(T+d)Z daug-cc-pVDZ daug-cc-pVTZ

average calculated bond lengths (Å)
Methods with effective core potentials (select basis sets)
CEP-31G CEP-31G* CEP-121G CEP-121G* LANL2DZ SDD cc-pVTZ-PP aug-cc-pVTZ-PP Def2TZVPP
hartree fock HF 2.1404
2
  2.1382
2
  2.1222
2
2.1172
2
    2.0413
2
ROHF                 2.0164
1
density functional BLYP                 2.0873
2
B1B95                 2.0476
2
B3LYP 2.1710
2
  2.1710
2
  2.1456
2
2.1450
2
    2.0647
2
B3LYPultrafine                 2.0647
2
B3PW91                 2.0552
2
mPW1PW91                 2.0509
2
M06-2X                 2.0554
2
PBEPBE                 2.0737
2
PBEPBEultrafine                 2.0737
2
PBE1PBE                 2.0514
2
HSEh1PBE                 2.0533
2
TPSSh                 2.0566
2
wB97X-D 2.1482
2
  2.1474
2
  2.1241
2
2.1200
2
    2.0435
2
B97D3                 2.0747
2
Moller Plesset perturbation MP2 2.1708
2
  2.1714
2
  2.1372
2
2.1785
2
    2.0438
2
MP2=FULL                 2.0428
2
ROMP2                 2.0550
1
MP3                 2.0427
2
MP3=FULL                 2.0428
2
MP4                 2.0389
1
MP4=FULL                 2.0615
2
B2PLYP                 2.0637
2
B2PLYP=FULL                 2.0629
2
B2PLYP=FULLultrafine                 2.0629
2
Configuration interaction CID                 2.0372
2
CISD                 2.0402
2
Quadratic configuration interaction QCISD                 2.0623
2
QCISD(T)                 2.0720
2
QCISD(T)=FULL                 2.0701
2
QCISD(TQ)                 2.0663
2
QCISD(TQ)=FULL                 2.0640
2
Coupled Cluster CCD                 2.0441
2
CCSD                 2.0558
2
CCSD=FULL                 2.0539
2
CCSD(T)                 2.0664
2
CCSD(T)=FULL                 2.0645
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.