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III.G.1.a.

Comparison of levels of theory for Be-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
composite G2 2.6733
1
G3 2.6733
1
G3B3 2.5952
1
G4 2.6864
1
CBS-Q 2.6710
1

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) TZVP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ
hartree fock HF 2.6019
1
2.8270
1
2.8270
1
2.8190
1
2.7846
1
2.7846
1
2.7693
1
2.7341
1
2.7341
1
2.7560
1
2.6250
1
2.7563
1
2.7329
1
2.7267
1
2.7333
1
2.7304
1
2.7260
1
ROHF   2.8270
1
2.8270
1
2.8190
1
2.7846
1
2.7846
1
2.7693
1
2.7341
1
2.7341
1
  2.6250
1
2.7563
1
2.7329
1
2.7267
1
2.7333
1
2.7304
1
2.7260
1
density functional LSDA 2.4889
1
2.6033
1
2.6033
1
2.5823
1
2.5752
1
2.5752
1
2.5741
1
2.5473
1
2.5473
1
2.5567
1
2.5052
1
2.5648
1
2.5448
1
  2.5450
1
2.5438
1
 
SVWN   2.6033
1
    2.5752
1
2.5752
1
2.5741
1
2.5473
1
2.5473
1
2.5567
1
  2.5648
1
2.5448
1
  2.5450
1
2.5438
1
 
BLYP 2.5212
1
2.6180
1
2.6180
1
2.6052
1
2.5953
1
2.5953
1
2.5953
1
2.5753
1
2.5753
1
2.5897
1
2.5386
1
2.5818
1
2.5734
1
       
B1B95 2.5382
1
2.6700
1
2.6700
1
2.6501
1
2.6489
1
    2.6150
1
2.6150
1
2.6307
1
2.5640
1
2.6321
1
2.6159
1
  2.6236
1
2.6133
1
 
B3LYP 2.5153
1
2.6136
1
2.6136
1
2.6000
1
2.5910
1
2.5910
1
2.5887
1
2.5669
1
2.5669
1
2.5816
1
2.5237
1
2.5761
1
2.5654
1
2.5600
1
2.5696
1
2.5632
1
2.5585
1
B3LYPultrafine         2.5910
1
                    2.6768
1
 
B3PW91 2.5211
1
2.6435
1
2.6435
1
2.6277
1
2.6194
1
2.6194
1
2.6150
1
2.5904
1
2.5904
1
2.6038
1
2.5379
1
2.6033
1
2.5864
1
       
mPW1PW91 2.5177
1
2.6384
1
2.6384
1
2.6230
1
2.6149
1
2.6149
1
2.6104
1
2.5865
1
2.5865
1
2.6000
1
2.5346
1
2.5993
1
2.5831
1
  2.5907
1
2.5813
1
 
M06-2X 2.5134
1
2.5967
1
2.5967
1
2.5838
1
2.5759
1
2.5759
1
2.5711
1
2.5486
1
2.5486
1
2.5694
1
2.5088
1
2.5630
1
2.5494
1
  2.5551
1
2.5474
1
 
PBEPBE 2.5157
1
2.6316
1
2.6316
1
2.6136
1
2.6067
1
2.6067
1
2.6047
1
2.5826
1
2.5826
1
2.5947
1
2.5415
1
2.5934
1
2.5795
1
  2.5869
1
2.5770
1
 
PBE1PBE 2.5151
1
2.6361
1
2.6361
1
2.6193
1
2.6120
1
2.6120
1
2.6077
1
2.5839
1
2.5839
1
2.5970
1
2.5341
1
2.5965
1
2.5813
1
  2.5884
1
2.5795
1
 
HSEh1PBE 2.5165
1
2.6385
1
2.6385
1
2.6202
1
2.6123
1
2.6123
1
2.6082
1
2.5844
1
2.5844
1
2.5972
1
2.5355
1
2.5974
1
2.5820
1
  2.5894
1
2.5802
1
 
TPSSh         2.6793
1
  2.6776
1
          2.6635
1
       
Moller Plesset perturbation MP2 2.5745
1
2.7386
1
2.7386
1
2.7410
1
2.6131
1
2.6131
1
2.6000
1
2.5608
1
2.5608
1
2.5686
1
2.5713
1
2.5960
1
2.5433
1
2.5273
1
2.5781
1
2.5396
1
2.5268
1
MP2=FULL 2.5727
1
2.7373
1
2.7373
1
2.7388
1
2.6038
1
2.6038
1
2.5896
1
2.5485
1
2.5485
1
2.5140
1
2.5681
1
2.5862
1
2.4912
1
2.4934
1
2.5284
1
2.4675
1
2.4892
1
ROMP2 2.4954
1
            2.5986
1
2.5986
1
  2.5575
1
  2.6116
1
       
MP3         2.5806
1
  2.6982
1
                   
MP3=FULL         2.6943
1
  2.6872
1
                   
MP4   2.7640
1
    2.5806
1
      2.5309
1
      2.5230
1
       
Configuration interaction CID   2.8214
1
2.8214
1
2.8333
1
2.6098
1
    2.5477
1
                 
CISD     3.0115
1
3.0887
1
2.7144
1
    2.6349
1
                 
Quadratic configuration interaction QCISD   3.0048
1
3.0048
1
3.0782
1
2.7152
1
2.7152
1
2.6959
1
2.6394
1
2.6394
1
2.6520
1
2.7186
1
2.6746
1
2.6280
1
  2.6630
1
2.6255
1
 
QCISD(T)         2.6986
1
          2.7020
1
2.6633
1
2.6171
1
  2.6522
1
2.6150
1
 
Coupled Cluster CCD   2.8214
1
2.8214
1
2.8332
1
2.6098
1
2.6098
1
2.5962
1
2.5477
1
2.5477
1
2.5632
1
2.6105
1
2.5841
1
2.5386
1
  2.5708
1
2.5355
1
 
CCSD         2.7167
1
            2.6727
1
2.6246
1
       
CCSD(T)         2.6990
1
          2.6997
1
2.6615
1
2.6141
1
2.6020
1
2.6499
1
2.6121
1
2.6019
1
CCSD(T)=FULL         2.6860
1
          2.6937
1
2.6502
1
2.5458
1
2.5593
1
2.5973
1
2.5133
1
2.5541
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 2.8013
1
2.7643
1
2.7469
1
2.7268
1
2.7949
1
2.7887
1
density functional B3LYP 2.6286
1
2.6193
1
2.6043
1
2.5962
1
2.5957
1
2.6000
1
Moller Plesset perturbation MP2 2.7600
1
2.6047
1
2.6653
1
2.5565
1
2.7188
1
2.7020
1
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.