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Comparison of levels of theory for O-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 2.1171
3
PM3 1.8058
3
PM6 1.7679
6
composite G2 1.7903
6
G3 1.7903
6
G3B3 1.7954
8
G3MP2 1.7691
1
G4 1.7921
8
CBS-Q 1.7844
8

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 1.7219
8
1.7698
6
1.7574
6
1.8006
6
1.7831
10
1.7800
6
1.7925
6
1.7785
8
1.7870
6
1.7694
6
1.7386
2
1.8150
8
1.7853
6
1.7813
5
1.7439
4
1.7884
6
1.7682
8
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 1.7327
8
1.7582
8
1.7546
8
1.7982
6
1.7913
8
1.7900
8
1.7996
8
1.7933
8
1.7937
8
1.7734
8
  1.7933
6
1.7934
8
1.7809
8
  1.7896
8
1.7858
6
     
SVWN   1.7852
8
    1.7942
10
1.7978
6
1.8013
10
1.8013
6
1.8012
6
1.7810
6
  1.7908
4
1.8018
6
1.7884
6
  1.7972
6
1.7858
6
     
BLYP 1.7584
8
1.7943
8
1.7764
8
1.8240
6
1.8029
12
1.8191
8
1.8320
8
1.8212
8
1.8226
8
1.8047
8
  1.8262
6
1.8280
6
1.8202
6
  1.8442
4
1.8761
2
     
B1B95 1.7355
8
1.7598
8
1.7567
8
1.8036
6
1.7949
8
1.7949
8
1.8021
8
1.7948
8
1.7956
8
1.7793
8
  1.8116
4
1.7907
8
1.7838
8
  1.7962
5
1.7893
6
  1.7442
1
1.7306
1
B3LYP 1.7426
8
1.7804
6
1.7668
6
1.7927
8
1.8015
8
1.7995
8
1.8104
8
1.8033
8
1.8119
7
1.7846
8
1.7563
2
1.8205
8
1.8004
8
1.7998
6
1.7608
5
1.8079
6
1.7915
8
1.7633
6
1.7474
1
1.7349
1
B3LYPultrafine   1.8699
2
    1.8016
8
1.8619
2
1.8704
2
1.8718
2
      1.8727
2
1.8680
2
1.8498
2
  1.8599
2
1.7986
8
     
B3PW91 1.7511
7
1.7891
5
1.7683
6
1.8067
6
1.8000
8
1.7981
8
1.8078
8
1.8007
8
1.8094
7
1.7833
7
  1.7993
6
1.8087
6
1.7978
6
  1.8171
4
1.8462
2
     
mPW1PW91 1.7472
7
1.7774
6
1.7618
7
1.8034
6
1.7964
8
1.7942
8
1.8035
8
1.7961
8
1.7973
8
1.7804
8
  1.7991
6
1.8047
6
1.7938
6
  1.7960
8
1.7919
6
     
M06-2X 1.7304
6
1.7848
4
1.7795
12
1.8140
4
1.7924
10
1.7945
6
1.8019
6
1.7970
6
1.7981
6
1.7820
6
  1.8065
4
1.7915
6
1.7855
6
  1.7971
6
1.7822
6
     
PBEPBE 1.7650
7
1.7896
8
1.7849
6
1.8411
4
1.8176
8
1.8163
8
1.8249
8
1.8207
8
1.8175
8
1.8020
8
1.7841
2
1.8209
6
1.8196
8
1.8093
8
  1.8194
6
1.8152
6
     
PBEPBEultrafine   1.8918
2
    1.8397
4
1.8812
2
1.8891
2
1.8903
2
      1.8917
2
1.8877
2
1.8666
2
  1.8776
2
1.8681
2
     
PBE1PBE 1.7373
6
1.7668
6
1.7668
6
1.8222
4
1.8009
10
1.8046
6
1.8114
6
1.8050
6
1.8067
6
1.7881
6
  1.8124
4
1.8052
6
1.7942
6
  1.8034
6
1.7924
6
     
HSEh1PBE 1.7376
6
1.7973
7
1.7668
6
1.8227
4
1.7996
10
1.8027
6
1.8101
10
1.8054
6
1.8071
6
1.7880
6
  1.8133
4
1.8052
6
1.7919
10
  1.8037
6
1.7930
6
     
TPSSh 1.7956
2
1.8781
2
1.8524
2
1.9071
2
1.8007
8
1.8667
2
1.8117
8
1.8750
2
1.8750
2
1.7887
12
  1.8749
2
1.8729
2
1.7947
8
  1.8627
2
1.8523
2
     
wB97X-D 1.7866
2
1.8654
2
1.7629
12
1.8942
2
1.7878
12
1.8548
2
1.8009
12
1.8641
2
1.7951
12
1.8383
2
  1.7976
12
1.8005
12
1.7854
12
  1.8525
2
1.7868
12
     
B97D3   1.7782
10
    1.7893
10
      1.7958
10
              1.7892
10
     
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
Moller Plesset perturbation MP2 1.7332
7
1.7727
6
1.7691
6
1.8080
6
1.8031
12
1.8038
8
1.8211
8
1.8044
12
1.8055
8
1.7925
8
  1.8194
10
1.8006
8
1.7985
8
1.7684
5
1.8166
7
1.7994
8
1.7703
5
1.7346
1
1.7371
1
MP2=FULL 1.7177
7
1.7732
6
1.7907
4
1.8371
4
1.8032
8
1.7983
8
1.8161
6
1.7983
8
1.8136
7
1.7946
6
  1.8095
6
1.8046
7
1.7885
7
1.7529
3
1.8068
8
1.7835
7
1.7515
2
1.7345
1
1.7348
1
MP3         1.8062
8
  1.8039
8
        1.8618
2
1.8641
2
1.8405
2
           
MP3=FULL   1.8627
2
1.8429
2
1.8997
2
1.8006
8
1.8583
2
1.8186
8
1.8599
2
1.8599
2
1.8331
2
  1.8602
2
1.8641
2
1.8302
2
  1.8502
2
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 1.7863
2
1.8714
2
1.8469
2
1.9064
2
1.8177
6
1.8643
2
1.8554
3
1.8721
2
1.8721
2
1.8475
2
  1.8735
2
1.8702
2
1.7963
6
  1.8649
2
1.8541
2
     
B2PLYP=FULL 1.7867
2
1.8291
3
1.8471
2
1.9066
2
1.8335
3
1.8638
2
1.8457
3
1.8718
2
1.8718
2
1.8442
2
  1.8730
2
1.8702
2
1.8472
2
  1.8612
2
1.8507
2
     
B2PLYP=FULLultrafine 1.7868
2
1.8717
2
1.8471
2
1.9065
2
1.8487
3
1.8638
2
1.8729
2
1.8717
2
1.8717
2
1.8442
2
  1.8729
2
1.8702
2
1.8472
2
  1.8612
2
1.8507
2
     
Configuration interaction CID   1.7899
4
1.7812
4
1.8244
4
1.7965
8
    1.7897
8
                       
CISD   1.7913
4
1.7823
4
1.8254
4
1.7984
8
1.7736
1
  1.7969
6
                       
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
Quadratic configuration interaction QCISD   1.8073
6
1.7910
4
1.8382
4
1.8126
8
1.8126
6
1.8189
8
1.8058
8
1.8124
7
1.7967
6
  1.8072
6
1.8090
8
1.7963
8
  1.8213
6
1.8004
6
     
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   1.7944
4
1.7846
4
1.8303
4
1.8029
8
1.8066
6
1.8161
6
1.7981
8
1.8070
6
1.7908
6
  1.8037
6
1.8038
7
1.7930
7
  1.8157
6
1.8081
4
  1.7851
1
1.7643
1
CCSD         1.8094
8
    1.7914
2
  1.8485
2
  1.8693
2
1.8113
6
1.7987
6
  1.8679
2
1.8512
2
     
CCSD=FULL         1.8649
2
        1.8383
2
  1.8679
2
1.8713
2
1.8355
2
  1.8567
2
1.8403
2
     
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 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)
CEP-31G CEP-31G* CEP-121G CEP-121G* LANL2DZ SDD
hartree fock HF 1.8273
6
1.7884
6
1.8027
6
1.7806
6
1.7797
8
1.8076
6
density functional B1B95 1.8010
2
1.7792
2
       
B3LYP 1.8327
6
1.8051
8
1.8153
6
1.8014
8
1.7970
6
1.8126
6
wB97X-D 1.9060
2
1.8591
2
1.8983
2
1.8567
2
1.8746
2
1.8983
2
Moller Plesset perturbation MP2 1.8376
6
1.7995
8
1.8147
6
1.8002
8
1.8033
6
1.8185
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.