return to home page

III.G.1.a.

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 2.3078
1
PM3 2.5609
2
PM6 1.3070
4
composite G2 2.4217
5
G3 2.4217
5
G3B3 2.3350
5
G4 2.2896
4
CBS-Q 2.4217
5

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-pCVDZ cc-pCVTZ
hartree fock HF 2.3174
5
2.4004
5
2.4004
5
2.4392
5
3.6334
9
2.4301
5
2.4194
5
2.4023
5
2.4023
5
2.4282
5
2.7852
1
2.4548
6
3.0224
4
3.0713
3
2.9972
4
3.0851
3
2.9967
4
2.9962
4
2.7920
1
2.7833
1
ROHF         3.1969
2
                             
density functional LSDA 2.1106
4
2.1307
4
2.1307
4
2.1459
4
2.1379
4
2.1379
4
2.1242
4
2.1029
4
2.1029
4
1.8113
3
  1.3514
2
2.8253
3
2.7924
3
2.9811
1
2.8173
3
2.8392
2
2.9786
1
2.7094
1
2.6932
1
SVWN   2.3648
5
    2.4978
5
1.3668
2
2.3707
5
1.3500
2
1.3500
2
1.3585
2
    2.7179
1
2.6930
1
  2.7174
1
2.6929
1
  2.7094
1
2.6932
1
BLYP 2.1380
4
2.1308
4
2.1308
4
2.1530
4
2.1430
4
2.1430
4
2.1196
4
2.1208
4
2.1208
4
2.1520
4
  1.3605
2
2.8813
2
2.8642
2
  2.7164
1
    2.7170
1
2.7103
1
B1B95 2.3001
5
2.3334
5
2.3334
5
2.3630
5
2.3537
5
2.3539
5
2.3390
5
2.3282
5
2.3282
5
2.3467
5
  1.3597
2
2.9208
4
2.8288
3
3.0750
2
2.8402
3
2.8779
2
3.0653
2
2.7253
1
2.7144
1
B3LYP 2.3056
5
2.3180
5
2.3180
5
2.3494
5
2.3369
5
2.3369
5
2.3223
5
2.3133
5
2.2155
4
2.3330
5
2.7009
1
2.4276
6
2.8951
4
2.9376
3
2.8690
4
2.9468
3
2.8745
4
2.8689
4
2.7086
1
2.7000
1
B3LYPultrafine         2.3369
5
              2.7120
1
2.6983
1
  2.7125
1
3.0210
3
  2.7086
1
2.7000
1
B3PW91 1.9348
3
2.1690
4
2.1690
4
2.1822
4
2.1745
4
2.1745
4
2.1622
4
2.1487
4
1.9527
3
2.1717
4
  1.3686
2
2.9432
2
2.9154
2
  2.7515
1
    2.7462
1
2.7322
1
mPW1PW91 2.2091
4
2.3500
5
2.2463
4
2.3769
5
2.3655
5
2.3655
5
2.3565
5
2.3427
5
2.3428
5
2.3572
5
  1.3678
2
3.0007
3
2.9786
3
  2.7502
2
2.7310
1
  2.7448
1
2.7324
1
M06-2X 1.3277
2
1.3720
2
1.3720
2
1.3646
2
2.4049
5
1.3607
2
1.3621
2
1.3466
2
1.3466
2
1.3599
2
  1.3496
2
2.7235
1
2.6915
1
  2.7213
1
2.6910
1
  2.7121
1
2.6898
1
PBEPBE 2.2165
4
2.3365
5
2.2324
4
2.2664
4
2.3529
5
2.3529
5
2.3420
5
2.3328
5
2.3328
5
2.3456
5
2.7276
1
1.3678
2
2.9193
4
2.9016
4
3.0642
2
2.7423
1
2.7255
1
3.0612
2
2.7390
1
2.7282
1
PBEPBEultrafine         2.7507
2
              2.7413
1
2.7261
1
  2.7425
1
2.7257
1
  2.7393
1
2.7284
1
PBE1PBE 2.6942
1
2.7580
1
2.7580
1
2.7613
1
3.1220
5
2.7527
1
2.7546
1
2.7321
1
2.7321
1
2.7473
1
  2.7306
1
2.7452
1
2.7263
1
  2.7444
1
2.7260
1
  2.7385
1
2.7274
1
HSEh1PBE 1.3486
2
1.3791
2
1.3791
2
1.3814
2
2.4018
5
1.3769
2
1.3778
2
1.3665
2
1.3665
2
1.3743
2
  1.3664
2
2.7459
1
2.7272
1
  2.7450
1
2.7269
1
  2.7393
1
2.7283
1
TPSSh         2.3641
5
  2.3613
5
            2.9382
4
           
Moller Plesset perturbation MP2 2.2113
4
2.3822
5
2.3822
5
2.4220
5
2.3999
5
2.3999
5
2.3921
5
2.3699
5
2.3699
5
2.3956
5
  2.4455
6
2.9898
4
3.0240
3
2.9520
4
2.9840
4
2.9554
4
2.9523
4
2.7657
1
2.7480
1
MP2=FULL 2.2084
4
2.3800
5
2.2771
4
2.3217
4
2.3930
5
2.3930
5
2.3848
5
2.3620
5
2.2683
4
2.2429
4
  1.3745
2
3.0463
3
2.9248
4
2.8639
4
2.7624
2
2.7127
1
2.9309
3
2.7496
1
2.7248
1
MP3         2.1855
4
  2.2151
4
                      2.7397
1
2.7276
1
MP3=FULL         2.3633
5
  2.3613
5
                         
MP4   2.2563
4
    2.3714
5
    2.7123
1
2.2499
4
    2.7130
1
2.7464
1
2.9245
4
  2.7444
1
2.7183
1
  2.7263
1
2.7177
1
MP4=FULL   2.7498
1
    2.7388
1
      2.7016
1
      2.7304
1
2.6860
1
  2.7238
1
2.6789
1
  2.7115
1
2.6963
1
B2PLYP         3.0808
3
                2.9203
2
           
Configuration interaction CID   1.9654
3
1.9654
3
1.9928
3
2.1626
4
    2.1323
4
                    2.7102
1
2.7021
1
CISD   1.3691
2
1.3691
2
1.9893
3
1.8225
3
    1.3465
2
                    2.7091
1
2.7000
1
Quadratic configuration interaction QCISD   2.3384
5
2.2384
4
2.2884
4
2.3580
5
2.2641
4
2.3517
5
2.3247
5
2.3247
5
2.2582
4
  1.3537
2
2.9301
4
2.9030
4
  2.7270
1
2.7000
1
  2.7092
1
2.7000
1
QCISD(T)         2.1539
4
    2.6928
1
      1.3537
2
2.9132
2
2.8831
2
  2.9070
2
2.8810
2
  2.7091
1
2.6993
1
Coupled Cluster CCD   2.2473
4
2.2473
4
2.2912
4
2.3635
5
2.2715
4
2.2662
4
2.3339
5
2.9922
3
2.2689
4
  1.3500
2
2.9419
4
2.9869
3
  3.0120
3
2.9887
3
  2.7102
1
2.7021
1
CCSD         2.1570
4
    2.6928
1
      2.7074
1
2.7284
1
2.7000
1
2.6984
1
2.7270
1
2.7000
1
2.6992
1
2.7092
1
2.7000
1
CCSD=FULL         2.7254
1
            2.7054
1
2.7125
1
2.6693
1
2.6232
1
2.7069
1
2.6625
1
2.6257
1
2.6971
1
2.6821
1
CCSD(T)   2.7379
1
    2.1550
4
2.7334
1
2.7384
1
2.6928
1
2.6928
1
  2.7047
1
1.3537
2
2.8531
3
2.8234
3
2.8820
2
2.8483
3
2.8219
3
2.8794
2
2.7091
1
2.6993
1
CCSD(T)=FULL         2.2227
4
            1.3528
2
2.7118
1
2.6670
1
2.8627
3
2.7061
1
2.6600
1
2.8680
3
2.6960
1
2.6792
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 2.5303
5
3.1573
4
2.4261
5
3.0168
4
2.4248
5
2.4203
5
density functional B1B95 2.9525
1
2.9539
1
       
B3LYP 2.5124
5
3.1326
4
2.3728
5
2.9468
4
2.3305
5
2.3319
5
Moller Plesset perturbation MP2 2.5261
5
3.1297
4
2.4065
5
2.9743
4
2.4079
5
2.3986
5
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.