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Comparison of levels of theory for H-Mg


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 2.2228
2
PM3 1.6944
4
PM6 1.7138
5
composite G2 1.7508
5
G3 1.7508
5
G3B3 1.7533
5
G3MP2 1.7178
2
G4 1.7415
5
CBS-Q 1.7508
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 Def2TZVPP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pCVDZ cc-pCVTZ
hartree fock HF 1.6220
4
1.7587
5
1.7536
5
1.7604
5
1.7507
5
1.7463
5
1.7379
5
1.7468
5
1.7429
4
1.7372
5
1.7152
3
1.7336
5
1.7271
5
1.7459
4
1.7390
4
1.7337
4
1.7362
4
1.7318
4
1.7298
4
1.7099
2
1.7066
2
ROHF   1.7502
1
1.7439
1
  1.7409
1
1.7362
1
1.7362
1
1.7363
1
                         
density functional LSDA 1.6485
5
1.7688
4
1.7654
4
1.7753
5
1.7606
5
1.7570
4
1.7496
4
1.7568
5
1.7532
4
1.7465
4
  1.7051
2
  1.7599
4
1.7460
4
1.7786
2
1.7496
4
1.7391
4
1.7688
2
   
BLYP 1.6751
4
1.7782
5
1.7675
5
1.7788
5
1.7498
5
1.7614
5
1.7549
5
1.7636
5
1.7587
4
1.7515
4
  1.7078
2
  1.7627
4
1.7524
4
  1.7139
2
1.7091
2
     
B1B95 1.6490
4
  1.7582
4
1.7660
4
1.7533
4
1.7504
4
1.7422
4
1.7500
4
1.7475
4
1.7412
4
  1.7006
2
  1.7517
4
1.7408
4
1.7709
2
1.7420
4
1.7339
4
1.7611
2
   
B3LYP 1.6561
4
1.7659
5
1.7560
5
1.7660
5
1.7534
5
1.7491
5
1.7427
5
1.7509
5
1.7465
4
1.7409
5
1.7021
2
1.7395
5
1.7288
5
1.7503
4
1.7406
4
1.7367
4
1.7411
4
1.7338
4
1.7303
4
1.7057
2
1.7010
2
B3LYPultrafine   1.7240
2
    1.7529
4
1.7081
2
1.7081
2
1.7071
2
      1.6971
2
  1.7064
2
1.7018
2
  1.7047
2
1.7153
3
     
B3PW91 1.6520
4
1.7720
5
1.7625
5
1.7692
5
1.7560
5
1.7520
5
1.7461
5
1.7526
5
1.7489
4
1.7435
5
  1.7031
2
  1.7531
4
1.7429
4
  1.7109
2
1.7062
2
     
mPW1PW91 1.6473
4
1.7697
5
1.7602
4
1.7667
4
1.7537
5
1.7497
5
1.7440
5
1.7501
5
1.7464
4
1.7409
4
  1.7010
2
  1.7506
4
1.7406
4
  1.7094
2
1.7048
2
     
M06-2X 1.5575
2
1.7113
2
1.7430
5
1.7092
2
1.7435
5
1.7005
2
1.7006
2
1.6989
2
1.6971
2
1.6960
2
  1.6893
2
  1.6988
2
1.6946
2
  1.6970
2
1.6935
2
     
PBEPBE 1.6680
4
1.7844
4
1.7741
4
1.7831
4
1.7688
4
1.7651
4
1.7575
4
1.7659
4
1.7619
4
1.7554
4
1.7167
2
1.7136
2
1.7417
5
1.7669
4
1.7557
4
1.7881
2
1.7205
2
1.7150
2
1.7772
2
   
PBEPBEultrafine   1.7431
2
    1.7270
2
1.7240
2
1.7241
2
1.7220
2
      1.7134
2
  1.7227
2
1.7158
2
  1.7204
2
1.7149
2
     
PBE1PBE 1.5667
2
  1.7269
2
1.7264
2
1.7564
5
1.7183
2
1.7147
2
1.7128
2
1.7100
2
1.7081
2
  1.7030
2
  1.7127
2
1.7076
2
  1.7108
2
1.7067
2
     
HSEh1PBE 1.5669
2
1.7715
5
1.7266
2
1.7259
2
1.7564
5
1.7142
2
1.7461
5
1.7123
2
1.7100
2
1.7078
2
  1.7028
2
  1.7122
2
1.7433
5
  1.7100
2
1.7061
2
     
TPSSh 1.5680
2
1.7342
2
1.7278
2
1.7271
2
1.7431
5
1.7145
2
1.7363
5
1.7119
2
1.7092
2
1.7324
5
  1.7019
2
  1.7118
2
1.7307
5
1.7058
2
1.7100
2
1.7060
2
1.7045
2
   
wB97X-D 1.5651
2
1.7371
2
1.7520
5
1.7248
2
1.7405
5
1.7144
2
1.7323
5
1.7133
2
1.7318
5
1.7080
2
  1.7270
5
  1.7310
5
1.7280
5
1.7049
2
1.7100
2
1.7253
5
1.7034
2
   
B97D3 1.5834
2
1.7741
5
1.7399
2
1.7373
2
1.7575
5
1.7250
2
1.7497
5
1.7238
2
1.7500
5
1.7190
2
1.7427
5
1.7152
2
  1.7235
2
1.7459
5
1.7173
2
1.7216
2
1.7553
5
1.7143
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-pCVDZ cc-pCVTZ
Moller Plesset perturbation MP2 1.6348
4
1.7727
5
1.7584
5
1.7742
5
1.7449
5
1.7401
5
1.7328
5
1.7400
5
1.7387
4
1.7295
5
  1.7292
5
1.7233
5
1.7429
4
1.7377
4
1.7327
5
1.7412
5
1.7336
4
1.7308
5
1.7056
2
1.7038
2
MP2=FULL 1.6609
4
1.7732
5
1.7590
4
1.7756
4
1.7550
5
1.7398
5
1.7326
5
1.7516
5
1.7383
4
1.7252
4
  1.6921
2
  1.7426
4
1.7243
4
1.7205
5
1.7158
3
1.6896
2
1.7081
4
1.7029
2
1.6930
2
MP3         1.7613
4
  1.7323
5
        1.6945
2
  1.7062
2
1.7077
2
           
MP3=FULL   1.7440
2
1.7311
2
1.7410
2
1.7491
5
1.7073
2
1.7276
5
1.7199
2
1.7037
2
1.6948
2
  1.6926
2
  1.7060
2
1.6926
2
  1.7075
2
1.6909
2
     
MP4   1.7884
5
    1.7651
5
    1.7355
3
1.7409
4
    1.6963
2
  1.7074
2
1.7419
5
  1.7146
2
1.7110
2
     
MP4=FULL   1.7487
2
    1.7289
2
      1.7051
2
        1.7071
2
1.6941
2
  1.7091
2
1.6923
2
     
B2PLYP 1.5614
2
1.7254
2
1.7190
2
1.7210
2
1.7513
5
1.7060
2
1.7062
2
1.7078
2
1.7026
2
1.7000
2
  1.6941
2
  1.7043
2
1.7273
5
  1.7048
2
1.7008
2
     
B2PLYP=FULL 1.5617
2
1.7252
2
1.7188
2
1.7211
2
1.7122
2
1.7058
2
1.7054
2
1.7077
2
1.7022
2
1.6983
2
  1.6930
2
  1.7042
2
1.6964
2
  1.7031
2
1.6952
2
     
B2PLYP=FULLultrafine 1.5617
2
1.7255
2
1.7188
2
1.7210
2
1.7126
2
1.7058
2
1.7058
2
1.7076
2
1.7021
2
1.6983
2
  1.6929
2
  1.7041
2
1.6964
2
  1.7030
2
1.6952
2
     
Configuration interaction CID   1.7899
4
1.7705
4
1.7917
4
1.7666
5
    1.7640
5
                         
CISD   1.7950
5
1.7740
4
1.7961
4
1.7707
5
    1.7677
4
                         
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   1.7963
5
1.7845
5
1.7978
4
1.7714
5
1.7483
5
1.7417
5
1.7683
5
1.7438
5
1.7331
4
  1.6995
2
  1.7473
5
1.7451
4
  1.7161
2
1.7127
2
     
QCISD(T)         1.7352
4
1.7251
3
1.7251
3
1.7417
3
      1.6994
2
  1.7482
4
1.7453
4
  1.7506
4
1.7425
4
     
QCISD(T)=FULL         1.7334
2
  1.7127
2
            1.7100
2
1.6963
2
1.7027
2
1.7115
2
1.6944
2
1.6863
2
   
QCISD(TQ)         1.7338
2
  1.7132
2
            1.7100
2
1.7121
2
1.7107
2
1.7171
2
1.7133
2
1.7113
2
   
QCISD(TQ)=FULL         1.7336
2
  1.7128
2
            1.7100
2
1.6965
2
1.7029
2
1.7118
2
1.6947
2
1.6866
2
   
Coupled Cluster CCD   1.7912
5
1.7712
4
1.7929
4
1.7671
5
1.7446
5
1.7379
5
1.7646
5
1.7418
4
1.7305
4
  1.6978
2
  1.7450
4
1.7433
4
  1.7480
4
1.7404
4
  1.7067
2
1.7084
2
CCSD         1.7714
5
1.7244
3
1.7244
3
1.7409
3
  1.7034
2
  1.6995
2
  1.7100
2
1.7115
2
1.7100
2
1.7161
2
1.7126
2
1.7107
2
   
CCSD=FULL         1.7326
2
        1.6984
2
  1.6976
2
  1.7100
2
1.6958
2
1.7019
2
1.7110
2
1.6937
2
1.6863
2
   
CCSD(T)         1.7340
2
1.7251
3
1.7250
3
1.7416
3
1.7085
2
1.7039
2
  1.6994
2
  1.7486
4
1.7456
4
1.7100
2
1.7510
4
1.7429
4
1.7112
2
1.7088
2
1.7100
2
CCSD(T)=FULL         1.7949
3
            1.6982
2
  1.7100
2
1.6963
2
1.7027
2
1.7115
2
1.6945
2
1.6864
2
1.7068
2
1.7002
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-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         1.7815
5
1.7562
5
1.7562
5
1.7510
5
1.7450
5
1.7489
5
density functional B1B95         1.7491
2
1.7355
3
       
B3LYP         1.7831
5
1.7615
5
1.7677
5
1.7598
5
1.7499
5
1.7541
5
wB97X-D         1.7513
2
1.7239
2
1.7229
2
1.7209
2
1.7136
2
1.7209
2
Moller Plesset perturbation MP2         1.7976
5
1.7709
5
1.7714
5
1.7580
5
1.7610
5
1.7633
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.