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III.G.1.a.

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 2.7023
1
PM3 1.7374
4
PM6 1.7128
4
composite G2 1.7710
6
G3 1.7710
6
G3B3 1.7859
8
G4 1.7736
6
CBS-Q 1.7739
7

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 1.7492
8
1.8334
6
1.7387
6
1.9107
6
1.7686
13
1.7607
6
1.8056
5
1.7651
8
1.7691
6
1.7509
6
1.7386
2
1.8064
6
1.7671
6
1.7606
5
1.7513
6
1.7972
6
1.7732
8
1.7549
5
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 1.7206
8
1.7465
8
1.7429
8
1.7807
6
1.7788
8
1.7775
8
1.7892
8
1.7821
8
1.7825
8
1.7625
8
  1.7576
4
1.7816
8
1.7707
8
1.7933
2
1.7792
8
1.7721
6
1.7935
2
   
SVWN   1.7575
6
    1.7788
8
1.7689
4
1.7859
8
1.7699
4
1.7698
4
1.7535
4
    1.7710
4
1.7630
4
  1.7705
4
1.7590
4
     
BLYP 1.7471
8
1.7829
8
1.7653
8
1.8075
6
1.8079
8
1.8071
8
1.8222
8
1.8104
8
1.8118
8
1.7941
8
  1.7898
4
1.8129
6
1.8068
6
  1.8041
2
       
B1B95 1.7277
8
1.7499
8
1.7468
8
1.7908
6
1.7850
8
1.7850
8
1.7944
8
1.7862
8
1.7870
8
1.7709
8
  1.7611
2
1.7815
8
1.7761
8
1.8027
2
1.7774
4
1.7757
5
1.8036
2
1.7442
1
1.7306
1
B3LYP 1.7341
8
1.7668
6
1.7529
6
1.7824
8
1.7909
8
1.7889
8
1.8022
8
1.7940
8
1.7994
6
1.7754
8
1.7563
2
1.8031
6
1.7906
8
1.7882
6
1.7770
8
1.7963
6
1.7829
8
1.7754
8
1.7474
1
1.7349
1
B3LYPultrafine         1.7910
8
                      1.7810
6
     
B3PW91 1.7299
6
1.7727
5
1.7544
6
1.7929
6
1.7892
8
1.7873
8
1.7993
8
1.7913
8
1.7978
6
1.7727
7
  1.7646
4
1.7955
6
1.7861
6
  1.7786
2
       
mPW1PW91 1.7270
6
1.7639
6
1.7530
6
1.7903
6
1.7860
8
1.7838
8
1.7952
8
1.7869
8
1.7881
8
1.7713
8
  1.7670
4
1.7920
6
1.7824
6
  1.7776
6
1.7669
4
     
M06-2X 1.7074
4
1.7199
2
1.7265
4
1.7434
2
1.7790
8
1.7688
4
1.7762
4
1.7684
4
1.7702
4
1.7584
4
  1.7594
2
1.7613
4
1.7627
4
  1.7744
4
1.7571
4
     
PBEPBE 1.7396
6
1.7781
8
1.7701
6
1.8162
4
1.8056
8
1.8043
8
1.8151
8
1.8100
8
1.8069
8
1.7917
8
1.7841
2
1.7854
4
1.8083
8
1.7994
8
1.8226
2
1.7902
4
1.7887
4
1.8238
2
   
PBEPBEultrafine         1.7982
2
                             
PBE1PBE 1.7126
4
1.7288
4
1.7288
4
1.7474
2
1.7870
8
1.7786
4
1.7855
4
1.7750
4
1.7776
4
1.7631
4
  1.7610
2
1.7762
4
1.7706
4
  1.7789
4
1.7674
4
     
HSEh1PBE 1.7128
4
1.7234
2
1.7287
4
1.7476
2
1.7852
8
1.7755
4
1.7856
4
1.7752
4
1.7777
4
1.7625
4
  1.7616
2
1.7760
4
1.7709
4
  1.7789
4
1.7676
4
     
TPSSh         1.7787
6
  1.7910
6
            1.7760
6
           
Moller Plesset perturbation MP2 1.7162
6
1.7542
6
1.7579
6
1.7867
6
1.7954
8
1.7933
8
1.8201
10
1.7908
8
1.7962
8
1.7819
8
  1.8046
8
1.7909
8
1.7867
7
1.7814
7
1.8182
7
1.7927
8
1.7960
7
1.7346
1
1.7371
1
MP2=FULL 1.7181
6
1.7546
6
1.7745
4
1.8051
4
1.7931
8
1.7882
8
1.8190
6
1.7894
8
1.8049
6
1.7814
6
  1.7759
4
1.7939
7
1.7789
7
1.7736
5
1.7870
6
1.7563
5
1.7968
4
1.7345
1
1.7348
1
MP3         1.7913
8
  1.7823
6
                         
MP3=FULL         1.7814
6
  1.8031
6
                         
MP4   1.7563
6
    1.7989
8
    1.7516
2
1.8158
6
        1.7930
8
           
B2PLYP         1.7944
4
                1.7690
4
           
B2PLYP=FULLultrafine         1.8187
1
                             
Configuration interaction CID   1.7701
4
1.7603
4
1.7957
4
1.7846
8
    1.7787
8
                       
CISD   1.7748
4
1.7644
4
1.8014
4
1.7878
8
1.7736
1
  1.7840
6
                       
Quadratic configuration interaction QCISD   1.8059
6
1.7679
3
1.8092
3
1.8018
7
1.7974
5
1.8075
7
1.7947
7
1.8007
6
1.7820
5
  1.7745
4
1.8018
8
1.7860
7
  1.7961
4
1.7738
4
     
QCISD(T)         1.8024
8
    1.7939
2
      1.7767
4
1.8056
6
1.7930
4
  1.8103
5
1.7914
5
     
Coupled Cluster CCD   1.7723
4
1.7632
4
1.7986
4
1.7899
8
1.7893
6
1.8225
6
1.7862
8
1.7911
6
1.7734
6
  1.7728
4
1.7880
8
1.7786
7
  1.8215
6
1.8148
4
  1.7851
1
1.7643
1
CCSD         1.7977
8
    1.7914
2
        1.7812
4
1.7749
4
           
CCSD(T)   1.7751
1
    1.7899
6
1.7872
2
1.7909
1
1.7833
2
1.7754
1
  1.7603
1
1.7763
4
1.8057
6
1.7871
6
1.7645
2
1.8093
5
1.7864
6
1.7680
2
1.7721
1
1.7526
1
CCSD(T)=FULL         1.7970
7
            1.7742
4
1.7834
5
1.7565
3
1.7578
2
1.7878
4
1.7551
2
1.7468
2
1.7693
1
1.7430
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 1.8008
5
1.7751
6
1.7696
5
1.7623
6
1.7677
8
1.8992
6
density functional B1B95 1.8010
2
1.7792
2
       
B3LYP 1.8258
6
1.7977
8
1.8046
6
1.7926
8
1.7820
6
1.8007
6
Moller Plesset perturbation MP2 1.8143
6
1.7908
8
1.7889
6
1.7893
8
1.7878
6
1.7961
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.