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III.G.1.a.

Comparison of levels of theory for Cl-Cl


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 1.9939
5
PM3 2.1373
6
PM6 2.0953
6
composite G2 2.2722
7
G3 2.2722
7
G3B3 2.3267
7
G3MP2 1.9892
1
G4 2.2562
5
CBS-Q 2.2722
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) 6-311+G(3df,2pd) TZVP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(D+d)Z cc-pV(T+d)Z aug-cc-pV(T+d)Z cc-pCVDZ cc-pCVTZ Sadlej_pVTZ
hartree fock HF 2.2553
7
2.3921
7
2.2711
7
2.3816
7
2.1929
9
2.2676
7
2.2690
7
2.2798
7
2.2798
7
2.2433
7
1.9742
2
1.9742
1
2.2710
7
2.2711
7
2.2483
7
2.1995
3
2.2707
7
2.2462
7
2.1982
3
1.9904
2
2.2181
5
2.6357
1
    2.0101
1
ROHF   2.6901
1
2.6622
1
2.7172
1
2.4001
3
2.6716
1
2.6750
1
2.6950
1
2.6950
1
      2.6684
1
2.6607
1
2.6449
1
2.6415
1
2.6664
1
2.6408
1
2.6381
1
  2.6403
1
2.6357
1
     
density functional LSDA 2.3011
7
2.3021
7
2.2745
7
2.3972
7
2.2721
7
2.2721
7
2.2722
7
2.2899
7
2.2899
7
2.2330
7
1.9767
1
1.9767
1
2.3347
4
2.2700
7
2.2426
7
2.2883
2
2.2586
7
2.2770
6
2.2829
2
1.9928
2
2.5967
1
2.5772
1
     
SVWN 2.1050
1
2.4039
7
2.0128
1
2.1777
1
2.3299
6
2.3304
4
2.2722
7
2.3508
4
2.3508
4
2.2876
4
1.9767
1
1.9767
1
2.0230
1
2.3272
4
2.2991
4
1.9852
1
2.3139
4
2.2921
4
1.9849
1
1.9928
1
2.5967
1
2.5772
1
     
BLYP 2.3756
7
2.4949
7
2.3808
7
2.5015
7
2.3836
7
2.3836
7
2.3827
7
2.4001
7
2.4002
7
2.3473
7
2.0411
1
2.0411
1
2.4495
4
2.3808
7
2.3565
7
2.0488
1
2.0787
2
2.0558
1
2.0484
1
2.0265
2
2.8013
1
2.7801
1
     
B1B95 2.3092
7
2.3198
7
2.2921
7
2.4141
7
2.2896
7
2.2901
7
2.3531
6
2.3062
7
2.3062
7
2.2565
7
1.9795
1
1.9795
1
2.3507
4
2.2903
7
2.2633
7
2.3182
2
2.2823
7
2.3835
5
2.3142
2
1.9940
2
2.3182
2
2.6391
1
     
B3LYP 2.3319
7
2.4486
7
2.3288
7
2.4469
7
2.3287
7
2.3287
7
2.3292
7
2.3452
7
2.3931
6
2.2962
7
2.0106
2
2.0106
1
2.3325
7
2.3281
7
2.3042
7
2.2497
3
2.3208
7
2.2990
7
2.2467
3
2.0118
2
2.2733
5
2.7016
1
    2.0501
1
B3LYPultrafine 2.1190
1
2.2326
1
2.0446
1
2.2036
1
2.3291
7
2.0417
1
2.0445
1
2.0563
1
2.0563
1
2.0165
1
2.0099
1
2.0099
1
2.3979
2
2.3916
4
2.3654
4
2.0167
1
2.3824
4
2.2610
5
2.0163
1
2.0112
1
2.7167
1
2.7016
1
     
B3PW91 2.3531
6
2.4273
7
2.3023
7
2.4224
7
2.3004
7
2.3004
7
2.3001
7
2.3142
7
2.3611
6
2.2656
7
1.9887
1
1.9887
1
2.3629
4
2.3000
7
2.2725
7
1.9964
1
2.0250
2
2.0024
1
1.9961
1
1.9998
2
2.6680
1
2.6528
1
     
mPW1PW91 2.3403
6
2.4155
7
2.3355
6
2.4090
7
2.2871
7
2.2871
7
2.2872
7
2.3008
7
2.3009
7
2.2530
7
1.9824
1
1.9824
1
2.3493
4
2.2870
7
2.2599
7
1.9889
1
2.2735
5
2.3128
4
1.9887
1
1.9957
2
2.6464
1
2.6319
1
     
M06-2X 2.3204
4
2.4383
4
2.3372
4
2.4358
4
2.2708
7
2.3316
4
2.3320
4
2.3458
4
2.3458
4
2.3020
4
1.9856
1
1.9856
1
2.3345
4
2.3327
4
2.3090
4
1.9908
1
2.3259
4
2.3046
4
1.9906
1
1.9988
2
2.6231
1
2.6136
1
     
PBEPBE 2.3831
6
2.4558
7
2.3799
6
2.4976
6
2.3320
7
2.3320
7
2.3323
7
2.3479
7
2.3479
7
2.2926
7
2.0059
2
2.0059
1
2.3936
4
2.3293
7
2.3005
7
2.3607
2
2.3773
4
2.2858
5
2.3545
2
2.0087
2
2.2414
3
2.6901
1
    2.0225
1
PBEPBEultrafine 2.1251
1
2.2375
1
2.0443
1
2.2082
1
2.3245
5
2.0415
1
2.0447
1
2.0558
1
2.0558
1
2.0116
1
2.0052
1
2.0052
1
2.3969
2
2.3920
4
2.3599
4
2.0128
1
2.3793
4
2.3528
4
2.0125
1
2.0080
1
2.7102
1
2.6901
1
     
PBE1PBE 2.3382
4
2.3524
4
2.3524
4
2.4564
4
2.2834
7
2.3452
4
2.3452
4
2.3596
4
2.3596
4
2.3055
4
1.9799
1
1.9799
1
2.3449
4
2.3437
4
2.3137
4
1.9873
1
2.3334
4
2.3081
4
1.9871
1
1.9941
1
2.6391
1
2.6247
1
     
HSEh1PBE 2.3418
4
2.4629
4
2.3578
4
2.4623
4
2.2885
7
2.3513
4
2.3513
4
2.3666
4
2.3666
4
2.3119
4
1.9820
1
1.9820
1
2.3517
4
2.3494
4
2.3204
4
1.9886
1
2.3390
4
2.3147
4
1.9880
1
1.9955
2
2.6492
1
2.6347
1
     
TPSSh   2.4865
2
2.3762
2
2.4918
2
2.1715
5
2.3786
2
2.1721
5
2.3936
2
        2.3798
2
2.3785
2
2.1581
5
  2.3693
2
2.3448
2
    2.6854
1
2.6716
1
     
Moller Plesset perturbation MP2 2.3656
5
2.4566
7
2.2848
7
2.4521
7
2.2827
7
2.2827
7
2.2851
7
2.2934
7
2.2935
7
2.2734
6
1.9845
1
1.9845
1
2.2780
7
2.2822
7
2.2372
7
2.1776
3
2.2868
7
2.2354
7
2.1757
3
2.0026
2
2.2578
4
2.5642
1
2.0244
2
1.9872
2
2.0407
1
MP2=FULL 2.3655
5
2.4569
7
2.3287
6
2.4895
6
2.2823
7
2.2823
7
2.2846
7
2.2928
7
2.3371
6
2.2692
6
1.9797
1
1.9797
1
2.3365
4
2.2817
7
2.2321
7
2.1737
3
2.2836
5
2.2255
5
2.2650
2
2.0016
2
2.2512
4
2.5526
1
2.0228
2
1.9835
2
 
ROMP2 2.5363
1
2.6508
1
2.6508
1
2.7576
1
2.6624
1
2.6624
1
2.6652
1
2.6813
1
2.6813
1
2.5835
1
    2.6427
1
2.6399
1
2.5859
1
  2.6444
1
      2.5801
1
2.5711
1
     
MP3 2.1126
1
2.2691
1
2.0289
1
2.2428
1
2.2904
7
2.0255
1
2.1683
5
2.0372
1
2.0372
1
2.0066
1
1.9968
1
1.9968
1
2.3418
2
2.3430
2
2.3064
2
1.9960
1
2.0513
1
2.0105
1
1.9961
1
2.0091
1
2.5992
1
2.5953
1
     
MP3=FULL         2.1682
5
  2.1690
5
          2.3417
2
2.3424
2
2.3021
2
          2.5943
1
2.5862
1
     
MP4 2.1231
1
2.4973
6
2.0410
1
2.2581
1
2.3028
7
2.0353
1
2.0392
1
2.0490
1
2.3618
6
2.0116
1
2.0039
1
2.0039
1
2.3618
4
2.3645
4
2.2587
7
2.0016
1
2.3718
4
2.3183
4
2.0019
1
2.0316
2
2.5962
1
2.5905
1
     
MP4=FULL 2.1229
1
2.5063
4
2.0414
1
2.2588
1
2.3696
4
2.0351
1
2.0393
1
2.0488
1
2.3825
4
2.0063
1
1.9989
1
1.9989
1
2.0464
1
2.3639
4
2.3126
4
1.9985
1
2.3704
4
2.3098
4
1.9982
1
  2.5898
1
2.5802
1
     
B2PLYP 2.3447
2
2.4866
2
2.3603
2
2.4895
2
2.2776
5
2.3634
2
2.3657
2
2.3823
2
2.3823
2
2.3272
2
2.0000
1
2.0000
1
2.3659
2
2.3617
2
2.0237
3
2.0046
1
2.3608
2
2.3288
2
2.0044
1
2.0072
1
2.6479
1
2.6370
1
     
B2PLYP=FULL 2.3447
2
2.4866
2
2.3601
2
2.4895
2
2.3632
2
2.3632
2
2.3655
2
2.3822
2
2.3822
2
2.3258
2
    2.3658
2
2.3614
2
2.3319
2
  2.3602
2
2.3262
2
    2.6458
1
2.6335
1
     
Configuration interaction CID 2.1288
1
2.4729
6
2.3233
6
2.4727
6
2.2780
7
2.0144
1
2.0171
1
2.2869
7
2.0252
1
1.9932
1
1.9831
1
1.9831
1
2.0261
1
2.0308
1
1.9952
1
1.9818
1
2.0346
1
1.9952
1
1.9816
1
  2.5976
1
2.5897
1
     
CISD 2.1300
1
2.4781
6
2.3258
6
2.4789
6
2.2805
7
  2.0192
1
2.3337
6
2.0273
1
1.9943
1
1.9843
1
1.9843
1
2.0279
1
2.0327
1
1.9964
1
1.9827
1
2.0364
1
1.9963
1
1.9825
1
  2.5993
1
2.5909
1
     
Quadratic configuration interaction QCISD 2.1300
1
2.4623
7
2.3394
6
2.4933
6
2.2946
7
2.3390
6
2.2989
7
2.3060
7
2.3060
7
2.2897
6
1.9974
1
1.9974
1
2.3523
4
2.2944
7
2.2535
7
1.9953
1
2.3619
4
2.3105
4
1.9953
1
2.0106
2
2.2014
3
2.5978
1
     
QCISD(T) 2.1305
1
2.2956
1
2.0453
1
2.2683
1
2.3044
7
2.0386
1
2.0428
1
2.0523
2
2.0529
1
2.0139
1
2.0060
1
2.0060
1
2.3633
4
2.3444
6
2.3004
6
2.0032
1
2.3530
6
2.3005
6
2.0035
1
  2.5989
1
2.5961
1
     
QCISD(T)=FULL         2.0384
1
  2.0429
1
            2.0544
1
2.0134
1
2.0000
1
2.0626
1
2.0124
1
1.9996
1
           
QCISD(TQ)   2.2989
1
2.0467
1
2.2722
1
2.0403
1
2.0402
1
2.0445
1
2.0542
1
2.0542
1
2.0160
1
2.0079
1
2.0079
1
2.0520
1
2.0567
1
2.0199
1
2.0050
1
2.0651
1
2.0217
1
2.0052
1
           
QCISD(TQ)=FULL         2.0400
1
  2.0444
1
            2.0563
1
2.0151
1
2.0017
1
2.0652
1
2.0142
1
             
Coupled Cluster CCD 2.1288
1
2.4823
6
2.3325
6
2.4825
6
2.2878
7
2.3316
6
2.3346
6
2.2982
7
2.3417
6
2.2851
6
1.9948
1
1.9948
1
2.3445
4
2.2889
7
2.2890
6
1.9931
1
2.3363
6
2.2873
6
1.9932
1
2.0091
2
2.2989
2
2.5943
1
     
CCSD 2.1300
1
2.2871
1
2.0334
1
2.2608
1
2.2935
7
2.0285
1
2.0320
1
2.0403
2
2.0404
1
2.0068
1
1.9971
1
1.9971
1
2.3508
4
2.3560
4
2.3116
4
2.2941
2
2.3607
4
2.3094
4
2.2920
2
  2.6033
1
2.5976
1
     
CCSD=FULL 2.1298
1
2.2872
1
2.0334
1
2.2611
1
2.3584
4
2.0280
1
2.0317
1
2.0390
1
2.0390
1
2.0014
1
1.9919
1
1.9919
1
2.3498
4
2.3554
4
2.3060
4
2.2901
2
2.3592
4
2.3010
4
2.2861
2
  2.5971
1
2.5868
1
     
CCSD(T) 2.1305
1
2.2959
1
2.0449
1
2.2686
1
2.3049
5
2.0379
2
2.0425
1
2.0519
2
2.0519
1
2.0138
1
2.0057
2
2.0058
1
2.3630
4
2.3028
7
2.2599
7
2.2960
2
2.3111
7
2.2601
7
2.2945
2
2.0351
2
2.3034
2
2.5960
1
2.0483
2
2.0075
2
 
CCSD(T)=FULL 2.1303
1
2.2964
1
2.0452
1
2.2693
1
2.3038
7
2.0382
1
2.0426
1
2.0516
1
2.0515
1
2.0084
1
2.0008
1
2.0008
1
2.3622
4
2.3037
5
2.2538
5
2.2924
2
2.3101
5
2.2512
5
2.2888
2
2.0338
2
2.2976
2
2.5861
1
2.0466
2
2.0042
2
 

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 2.3774
7
2.2642
7
2.3766
7
2.2634
7
2.3793
7
2.3864
7
density functional LSDA 2.1913
1
2.0353
1
2.1923
1
2.0338
1
2.2117
1
2.2045
1
SVWN 2.1913
1
2.0353
1
2.1923
1
2.0338
1
2.2117
1
2.2045
1
BLYP 2.2355
1
2.0838
1
2.2353
1
2.0817
1
2.2543
1
2.2588
1
B1B95 2.1847
2
2.0301
1
2.1812
1
2.0255
1
2.2049
1
2.2025
1
B3LYP 2.4493
7
2.3264
7
2.4480
7
2.3246
7
2.4515
7
2.4524
7
B3LYPultrafine 2.2019
1
2.0502
1
2.2026
1
2.0485
1
2.2252
1
2.2303
1
B3PW91 2.1844
1
2.0312
1
2.1853
1
2.0299
1
2.2095
1
2.2133
1
mPW1PW91 2.1756
1
2.0232
1
2.1767
1
2.0220
1
2.2012
1
2.2055
1
M06-2X 2.1685
1
2.0196
1
2.1709
1
2.0183
1
2.1884
1
2.1931
1
PBEPBE 2.2077
1
2.0507
1
2.2079
1
2.0491
1
2.2298
1
2.2330
1
PBEPBEultrafine 2.2079
1
2.0496
1
2.2081
1
2.0479
1
2.2310
1
2.2345
1
PBE1PBE 2.1737
1
2.0205
1
2.1749
1
2.0193
1
2.1991
1
2.2037
1
HSEh1PBE 2.1775
1
2.0229
1
2.1785
1
2.0217
1
2.2025
1
2.2071
1
Moller Plesset perturbation MP2 2.4484
7
2.2719
7
2.4477
7
2.2721
7
2.4430
7
2.4488
7
MP2=FULL 2.2151
1
2.0233
1
2.2192
1
2.0235
1
2.2344
1
2.2474
1
MP3 2.2348
1
2.0361
1
2.2342
1
2.0352
1
2.2553
1
2.2591
1
MP4 2.2491
1
2.0431
1
2.2484
1
2.0426
1
2.2708
1
2.2748
1
MP4=FULL 2.2491
1
2.0431
1
2.2484
1
2.0426
1
2.2708
1
2.2765
1
B2PLYP 2.2038
1
2.0374
1
2.2063
1
2.0367
1
2.2262
1
2.2342
1
Configuration interaction CID 2.2356
1
2.0249
1
2.2300
1
2.0231
1
2.2585
1
2.2551
1
CISD 2.2412
1
2.0260
1
2.2358
1
2.0244
1
2.2645
1
2.2605
1
Quadratic configuration interaction QCISD 2.2527
1
2.0377
1
2.2514
1
2.0370
1
2.2766
1
2.2773
1
QCISD(T) 2.2581
1
2.0461
1
2.2582
1
2.0458
1
2.2833
1
2.2858
1
QCISD(TQ) 2.2612
1
2.0478
1
2.2617
1
2.0475
1
2.2858
1
2.2881
1
Coupled Cluster CCD 2.2454
1
2.0356
1
2.2429
1
2.0344
1
2.2689
1
2.2694
1
CCSD 2.2526
1
2.0375
1
2.2511
1
2.0367
1
2.2763
1
2.2767
1
CCSD=FULL 2.2526
1
2.0375
1
2.2511
1
2.0367
1
2.2763
1
2.2761
1
CCSD(T) 2.2584
1
2.0460
1
2.2585
1
2.0456
1
2.2834
1
2.2858
1
CCSD(T)=FULL 2.2584
1
2.0460
1
2.2585
1
2.0456
1
2.2834
1
2.2875
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.