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Comparison of levels of theory for Mg-O


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 2.0657
5
PM3 1.8023
5
PM6 1.7853
8
composite G2 1.8060
8
G3 1.8059
8
G3B3 1.8096
10
G3MP2 1.7691
1
G4 1.8034
10
CBS-Q 1.8002
10

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 1.7320
10
1.7917
8
1.7787
8
1.8234
8
1.7831
10
1.7982
8
1.8083
8
1.7953
10
1.8058
8
1.7859
8
1.7386
2
1.8233
10
1.7859
14
1.8036
8
1.7970
7
1.7439
4
1.8031
8
1.7820
10
1.7450
4
1.7426
1
1.7159
1
ROHF   1.7269
1
1.7248
1
  1.7515
2
1.7621
1
1.7821
1
1.7655
1
                         
density functional LSDA 1.7437
10
1.7746
10
1.7717
10
1.8231
8
1.8040
10
1.8029
10
1.8116
10
1.8076
10
1.8079
10
1.7857
10
  1.8116
8
  1.8069
10
1.7926
10
  1.8022
10
1.7993
8
     
BLYP 1.7695
10
1.8142
10
1.7943
10
1.8492
8
1.8145
14
1.8322
10
1.8440
10
1.8361
10
1.8372
10
1.8171
10
  1.8448
8
  1.8431
8
1.8336
8
  1.8578
6
1.8760
4
     
B1B95 1.7460
10
1.8442
2
1.7742
10
1.8287
8
1.8079
10
1.8079
10
1.8147
10
1.8098
10
1.8105
10
1.7916
10
  1.8311
6
  1.8057
10
1.7958
10
  1.8134
7
1.8033
8
  1.7442
1
1.7306
1
B3LYP 1.7534
10
1.8039
8
1.7878
8
1.8154
10
1.8015
8
1.8128
10
1.8228
10
1.8181
10
1.8264
9
1.7974
10
1.7563
2
1.8321
10
1.7960
14
1.8144
10
1.7998
6
1.7608
5
1.8221
8
1.8042
10
1.7633
6
1.7474
1
1.7349
1
B3LYPultrafine   1.8722
4
    1.8144
10
1.8639
4
1.8712
4
1.8744
4
      1.8754
4
  1.8692
4
1.8517
4
  1.8622
4
1.8099
10
     
B3PW91 1.7605
9
1.8139
7
1.7892
8
1.8314
8
1.8129
10
1.8114
10
1.8201
10
1.8155
10
1.8239
9
1.7974
9
  1.8183
8
  1.8240
8
1.8109
8
  1.8319
6
1.8487
4
     
mPW1PW91 1.7566
9
1.8010
8
1.7811
9
1.8282
8
1.8093
10
1.8076
10
1.8160
10
1.8112
10
1.8121
10
1.7929
10
  1.8170
8
  1.8203
8
1.8070
8
  1.8084
10
1.8059
8
     
M06-2X 1.7435
8
1.8099
6
1.7811
10
1.8410
6
1.8028
12
1.8096
8
1.8163
8
1.8139
8
1.8148
8
1.7958
8
  1.8257
6
  1.8085
8
1.7991
8
  1.8108
8
1.7970
8
     
PBEPBE 1.7746
9
1.8102
10
1.8047
8
1.8684
6
1.8302
10
1.8291
10
1.8373
10
1.8346
10
1.8321
10
1.8139
10
1.7841
2
1.8391
8
1.8044
14
1.8327
10
1.8208
10
  1.8343
8
1.8285
8
     
PBEPBEultrafine   1.8920
4
    1.8531
6
1.8806
4
1.8877
4
1.8902
4
      1.8926
4
  1.8863
4
1.8666
4
  1.8780
4
1.8681
4
     
PBE1PBE 1.7503
8
1.8485
2
1.7872
8
1.8492
6
1.8110
12
1.8188
8
1.8252
8
1.8216
8
1.8229
8
1.8019
8
  1.8319
6
  1.8207
8
1.8073
8
  1.8172
8
1.8063
8
     
HSEh1PBE 1.7506
8
1.8141
9
1.7872
8
1.8498
6
1.8100
12
1.8175
8
1.8196
12
1.8222
8
1.8234
8
1.8020
8
  1.8329
6
  1.8208
8
1.8012
12
  1.8176
8
1.8069
8
     
TPSSh 1.7963
4
1.8801
4
1.8545
4
1.9089
4
1.8145
10
1.8682
4
1.8243
10
1.8772
4
1.8772
4
1.7977
14
  1.8776
4
  1.8739
4
1.8067
10
  1.8649
4
1.8543
4
     
wB97X-D 1.7885
4
1.8702
4
1.7756
14
1.8988
4
1.7987
14
1.8592
4
1.8107
14
1.8693
4
1.8065
14
1.8421
4
  1.8086
14
  1.8102
14
1.7946
14
  1.8569
4
1.7868
12
     
B97D3 1.8098
2
1.7982
12
1.8701
2
1.9262
2
1.8049
12
1.8832
2
1.8158
12
1.8934
2
1.8121
12
1.8653
2
1.8081
14
1.8972
2
  1.8879
2
1.8020
12
  1.8819
2
1.8032
8
     
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 1.7435
9
1.8003
8
1.7915
8
1.8373
8
1.8031
12
1.8189
10
1.8346
10
1.8155
14
1.8208
10
1.8067
10
  1.8310
12
1.8055
14
1.8168
10
1.7985
8
1.7684
5
1.8320
9
1.8136
10
1.7703
5
1.7346
1
1.7371
1
MP2=FULL 1.7317
9
1.8009
8
1.8136
6
1.8667
6
1.8182
10
1.8143
10
1.8332
8
1.8148
10
1.8285
9
1.8096
8
  1.8289
8
  1.8217
9
1.8028
9
1.7529
3
1.8216
10
1.8000
9
1.7515
2
1.7345
1
1.7348
1
MP3         1.8189
10
  1.8184
10
        1.8681
4
  1.8680
4
1.8451
4
           
MP3=FULL   1.8687
4
1.8478
4
1.9067
4
1.8143
10
1.8636
4
1.8294
10
1.8652
4
1.8652
4
1.8382
4
  1.8666
4
  1.8680
4
1.8353
4
  1.8581
4
1.8349
2
     
MP4   1.7815
6
    1.8045
8
    1.7516
2
1.8209
6
    1.8817
2
  1.8810
2
1.8059
10
  1.8819
2
1.8654
2
     
MP4=FULL   1.8849
2
    1.8740
2
      1.8775
2
        1.8809
2
1.8457
2
  1.8703
2
1.8534
2
     
B2PLYP 1.7884
4
1.8742
4
1.8495
4
1.9097
4
1.8305
8
1.8667
4
1.8639
5
1.8749
4
1.8749
4
1.8498
4
  1.8770
4
  1.8719
4
1.8111
8
  1.8680
4
1.8566
4
     
B2PLYP=FULL 1.7888
4
1.8484
5
1.8497
4
1.9099
4
1.8476
5
1.8663
4
1.8576
5
1.8746
4
1.8746
4
1.8465
4
  1.8765
4
  1.8719
4
1.8498
4
  1.8652
4
1.8530
4
     
B2PLYP=FULLultrafine 1.7888
4
1.8745
4
1.8496
4
1.9098
4
1.8567
5
1.8663
4
1.8741
4
1.8746
4
1.8746
4
1.8464
4
  1.8764
4
  1.8718
4
1.8498
4
  1.8651
4
1.8529
4
     
Configuration interaction CID   1.8163
6
1.8039
6
1.8519
6
1.8099
10
    1.8051
10
                         
CISD   1.8175
6
1.8048
6
1.8528
6
1.8114
10
1.7736
1
  1.8145
8
                         
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   1.8266
8
1.8138
6
1.8678
6
1.8253
10
1.8285
8
1.8320
10
1.8204
10
1.8272
9
1.8120
8
  1.8260
8
  1.8231
10
1.8081
10
  1.8359
8
1.8157
8
     
QCISD(T)         1.8132
8
    1.8350
4
      1.8105
6
  1.8181
6
1.8096
4
  1.8251
6
1.8065
6
     
QCISD(T)=FULL         1.8718
2
  1.8803
2
            1.8791
2
1.8421
2
  1.8650
2
1.8484
2
     
Coupled Cluster CCD   1.8216
6
1.7846
4
1.8303
4
1.8167
10
1.8229
8
1.8318
8
1.7981
8
1.8238
8
1.8067
8
  1.8223
8
  1.8038
7
1.7930
7
  1.8302
8
1.8247
6
  1.7851
1
1.7643
1
CCSD         1.8224
10
    1.7914
2
  1.8524
4
  1.8751
4
  1.8278
8
1.7987
6
  1.8725
4
1.8512
2
     
CCSD=FULL         1.8694
4
        1.8427
4
  1.8737
4
  1.8745
4
1.8399
4
  1.8642
4
1.8441
4
     
CCSD(T)   1.7751
1
    1.8104
8
1.8297
4
1.7909
1
1.8290
4
1.7754
1
  1.7603
1
1.8099
6
  1.8171
6
1.7991
6
1.7645
2
1.8242
6
1.8056
6
1.7680
2
1.7721
1
1.7526
1
CCSD(T)=FULL         1.8074
7
            1.8080
6
  1.8104
7
1.7904
5
1.7578
2
1.8131
6
1.8012
4
1.7468
2
1.7693
1
1.7430
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         1.8494
8
1.8051
8
1.8259
8
1.7982
8
1.8008
10
1.8300
8
density functional B1B95         1.8010
2
1.7792
2
       
B3LYP         1.8565
8
1.8188
10
1.8404
8
1.8155
10
1.8208
8
1.8371
8
wB97X-D         1.9151
4
1.8637
4
1.9043
4
1.8613
4
1.8821
4
1.9032
4
Moller Plesset perturbation MP2         1.8666
8
1.8172
10
1.8444
8
1.8168
10
1.8309
8
1.8471
8
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.