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Comparison of levels of theory for Li-Li


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 2.3409
5
PM3 2.7266
5
PM6 1.5748
7
composite G2 2.8974
6
G3 2.8974
6
G3B3 2.8516
6
G4 2.9394
8
CBS-Q 2.8974
6

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-pCVDZ cc-pCVTZ
hartree fock HF 2.8511
6
2.9555
6
2.9555
6
2.9727
6
3.4776
9
2.9611
6
2.9632
6
2.9317
6
2.9317
6
2.9515
6
2.7852
1
2.9828
9
2.9502
9
2.9590
6
2.9326
6
2.9323
6
2.9552
6
2.9335
6
2.9325
6
2.7920
1
2.7833
1
ROHF   2.8922
2
2.8922
2
2.9045
2
3.0078
3
2.8985
2
2.9044
2
2.8691
2
2.8691
2
    2.8736
2
  2.8961
2
2.8679
2
2.8675
2
2.8890
2
2.8681
2
2.8676
2
   
density functional LSDA 2.8255
6
2.8658
6
2.8658
6
2.8799
6
2.8738
6
2.8738
6
2.8740
6
2.8375
6
2.8375
6
2.8460
6
  2.8373
6
  2.8635
6
2.8326
6
  2.8611
6
2.8325
6
  2.7094
1
2.6932
1
BLYP 2.8447
6
2.8602
6
2.8602
6
2.8789
6
2.9134
9
2.8697
6
2.8707
6
2.8532
6
2.8532
6
2.8582
6
  2.8612
6
  2.8553
6
2.8487
6
  2.7164
1
    2.7170
1
2.7103
1
B1B95 2.8327
6
2.8799
6
2.8799
6
2.9001
6
2.8935
6
2.8935
6
2.9308
4
2.8656
6
2.8656
6
2.8799
6
  2.8647
6
  2.8842
6
2.8634
6
  2.8837
6
2.8634
6
  2.7253
1
2.7144
1
B3LYP 2.8302
6
2.8583
6
2.8583
6
2.8765
6
2.8679
6
2.8679
6
2.8688
6
2.8458
6
2.8458
6
2.8542
6
2.7009
1
2.9121
9
2.9151
9
2.8551
6
2.8416
6
2.8334
6
2.8559
6
2.8617
6
2.8376
6
2.7086
1
2.7000
1
B3LYPultrafine   2.8850
5
    2.8680
6
2.8970
5
2.8974
5
2.8740
5
      2.8784
5
  2.8551
6
2.8416
6
  2.8559
6
2.9268
8
  2.7086
1
2.7000
1
B3PW91 2.8450
6
2.9008
6
2.9008
6
2.9140
6
2.9060
6
2.9060
6
2.9064
6
2.8802
6
2.8802
6
2.8891
6
  2.8771
6
  2.8969
6
2.8754
6
  2.7515
1
    2.7462
1
2.7322
1
mPW1PW91 2.8414
6
2.8975
6
2.8975
6
2.9119
6
2.9036
6
2.9036
6
2.9042
6
2.8799
6
2.8799
6
2.8889
6
  2.8753
6
  2.8947
6
2.8752
6
  2.8949
6
2.8754
6
  2.7448
1
2.7324
1
M06-2X 2.8392
6
2.8810
6
3.7787
9
2.9154
6
2.9450
8
2.9087
6
2.9098
6
2.8762
6
2.8762
6
2.8948
6
  2.8745
6
  2.9089
6
2.8763
6
  2.9069
6
2.8765
6
  2.7121
1
2.6898
1
PBEPBE 2.8474
6
2.8836
6
2.8836
6
2.8998
6
2.8923
6
2.8923
6
2.8929
6
2.8729
6
2.8729
6
2.8775
6
2.7276
1
2.8724
6
2.9249
9
2.8816
6
2.8673
6
  2.8831
6
2.8673
6
  2.7390
1
2.7282
1
PBEPBEultrafine   2.9098
5
    2.8925
6
2.9209
5
2.9210
5
2.9007
5
      2.8999
5
  2.8817
6
2.8675
6
  2.8833
6
2.8674
6
  2.7393
1
2.7284
1
PBE1PBE 2.8375
6
2.8893
6
2.8893
6
2.9043
6
3.0442
8
2.8971
6
2.8976
6
2.8732
6
2.8732
6
2.8819
6
  2.8693
6
  2.8874
6
2.8684
6
  2.8877
6
2.8692
6
  2.7385
1
2.7274
1
HSEh1PBE 2.8395
6
2.9444
9
2.8895
6
2.9048
6
2.9382
8
2.8973
6
2.9315
8
2.8740
6
2.8740
6
2.8822
6
  2.8707
6
  2.8874
6
2.9288
9
  2.8877
6
2.8695
6
  2.7393
1
2.7283
1
TPSSh   2.9264
5
2.9264
5
2.9532
5
2.9498
9
2.9455
5
2.9481
9
2.9188
5
  2.9495
4
  2.9130
5
  2.9309
5
2.9246
9
  2.9314
5
2.9145
5
     
wB97X-D     2.9342
9
  2.9349
9
  2.9335
9
  2.9188
9
    2.9164
9
  2.9335
9
2.9169
9
    2.9170
9
     
B97D3   2.9443
9
    2.9471
9
  2.9460
9
  2.9369
9
  2.9350
9
      2.9345
9
    3.1131
9
     
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-pCVDZ cc-pCVTZ
Moller Plesset perturbation MP2 2.8540
6
2.9367
6
2.9367
6
2.9664
6
2.9624
4
2.9334
6
2.9353
6
2.9536
4
2.8953
6
2.9208
6
  2.9435
8
2.9440
9
2.9379
6
2.8963
6
2.8914
6
2.9320
6
2.8965
6
2.8920
6
2.7657
1
2.7480
1
MP2=FULL 2.8497
6
2.9337
6
2.9337
6
2.9621
6
2.9247
6
2.9247
6
2.9257
6
2.8846
6
2.8846
6
2.8359
6
  2.9055
6
  2.9243
6
2.8634
6
2.8030
6
2.9134
6
2.8561
6
2.8103
6
2.7496
1
2.7248
1
ROMP2 2.7580
2
2.8748
2
2.8748
2
2.9027
2
2.8673
2
2.8673
2
2.8717
2
2.8249
2
2.8249
2
2.8530
2
  2.8460
2
  2.8719
2
2.8272
2
  2.8639
2
       
MP3         2.9223
6
  2.9550
8
        2.9334
5
  2.9584
5
2.9148
5
        2.7397
1
2.7276
1
MP3=FULL         2.9492
9
  2.9485
9
        2.9301
5
  2.9449
5
2.8803
5
           
MP4   2.9208
6
    2.9186
6
    2.7123
1
2.8774
6
    2.8947
6
  2.9209
6
2.9157
7
  2.9159
6
2.8807
6
  2.7263
1
2.7177
1
MP4=FULL   2.9177
6
    2.9095
6
      2.8669
6
        2.9068
6
2.8457
6
  2.8968
6
2.8376
6
  2.7115
1
2.6963
1
B2PLYP 2.8691
5
2.9101
5
2.9101
5
2.9373
5
2.9806
8
2.9205
5
2.9212
5
2.8899
5
2.8899
5
2.9041
5
  2.8951
5
  2.9133
5
2.8973
7
  2.9110
5
2.8887
5
     
B2PLYP=FULL 2.8675
5
2.9091
5
2.9091
5
2.9359
5
2.9177
5
2.9177
5
2.9176
5
2.8861
5
2.8861
5
2.8755
5
  2.8934
5
  2.9083
5
2.8771
5
  2.9050
5
2.8731
5
     
Configuration interaction CID   2.9156
6
2.9156
6
2.9606
6
2.9154
6
    2.8722
6
                      2.7102
1
2.7021
1
CISD   2.9676
4
2.9676
4
3.0149
4
2.9177
6
    2.8746
6
                      2.7091
1
2.7000
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-pCVDZ cc-pCVTZ
Quadratic configuration interaction QCISD   2.9221
6
2.9221
6
2.9662
6
2.9190
6
2.9190
6
2.9207
6
2.8758
6
2.8758
6
2.9035
6
  2.8889
6
  2.9200
6
2.8796
6
  2.9163
6
2.8801
6
  2.7092
1
2.7000
1
QCISD(T)         2.9216
6
    2.6928
1
      2.8898
6
  2.9229
6
2.8821
6
  2.9192
6
2.8825
6
  2.7091
1
2.6993
1
QCISD(T)=FULL         2.9505
5
  2.9504
5
            2.9481
5
2.8830
5
2.8118
5
2.9389
5
2.8742
5
2.8204
5
   
QCISD(TQ)=FULL         2.9517
5
  2.9515
5
            2.9495
5
2.8839
5
2.8124
5
2.9401
5
2.8748
5
     
Coupled Cluster CCD   2.9156
6
2.9156
6
2.9607
6
2.9154
6
2.9154
6
2.9174
6
2.8722
6
2.8722
6
2.9001
6
  2.8916
6
  2.9160
6
2.8758
6
  2.9120
6
2.8760
6
  2.7102
1
2.7021
1
CCSD         2.9206
6
    2.6928
1
      2.8896
6
  2.9220
6
2.8818
6
2.8785
6
2.9180
6
2.8816
6
2.8792
6
2.7092
1
2.7000
1
CCSD=FULL         2.9123
6
            2.8868
6
  2.9082
6
2.8483
6
2.7812
6
2.8993
6
2.8395
6
2.7883
6
2.6971
1
2.6821
1
CCSD(T)   2.7379
1
    2.9222
6
2.7334
1
2.7384
1
2.6928
1
2.6928
1
  2.7047
1
2.8901
6
  2.9237
6
2.8828
6
2.8797
6
2.9200
6
2.8832
6
2.8806
6
2.7091
1
2.6993
1
CCSD(T)=FULL         2.9133
6
            2.8872
6
  2.9094
6
2.8475
6
2.7803
6
2.9008
6
2.8389
6
2.7878
6
2.6960
1
2.6792
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-pCVDZ cc-pCVTZ

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         3.1174
6
3.1133
6
2.9596
6
2.9447
6
2.9725
6
2.9644
6
density functional B1B95         2.9525
1
2.9539
1
       
B3LYP         3.0948
6
3.0913
6
2.9134
6
2.8999
6
2.8677
6
2.8734
6
Moller Plesset perturbation MP2         3.1198
6
3.0821
6
2.9492
6
2.9086
6
2.9642
6
2.9500
6
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.