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III.G.1.a.

Comparison of levels of theory for Be-Be


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 1.9465
5
PM3 1.9696
5
PM6 1.2844
5
composite G2 2.6607
6
G3 2.2697
5
G3B3 2.6137
4
G4 2.2351
4
CBS-Q 2.2691
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 cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pCVDZ cc-pCVTZ
hartree fock HF 2.5995
4
2.7088
5
2.7088
5
2.6342
5
2.6867
9
2.6220
5
2.9381
5
2.9891
5
3.0428
5
2.6046
5
1.7800
1
2.7201
5
3.9121
5
3.1506
5
3.1483
5
3.4635
4
3.1721
5
3.4501
4
   
ROHF 2.4581
1
2.2489
2
2.2489
2
2.2281
2
2.2179
3
2.2063
2
2.2868
2
2.2336
2
2.2336
2
2.3489
1
  2.0386
1
2.2421
2
2.2366
2
2.2379
2
3.5292
2
3.3377
2
3.5008
2
   
density functional LSDA 2.1711
4
2.2056
4
2.2056
4
2.2038
4
2.1965
4
2.1965
4
2.1971
4
2.1842
4
2.1842
4
2.1924
4
  2.1484
2
2.2017
4
2.1863
4
2.1754
1
2.2025
4
2.1867
3
2.1810
1
   
SVWN   2.1654
5
    2.1572
5
2.2003
2
2.1586
5
2.1868
2
2.1868
2
2.1940
2
    2.2041
2
2.1874
2
  2.2038
2
2.1871
2
     
BLYP 2.2968
4
2.2458
5
2.2458
5
2.2445
5
2.2375
5
2.2375
5
2.2338
5
2.2224
5
2.1969
5
2.2915
5
  2.2412
2
2.2370
5
2.2414
4
  2.0195
1
       
B1B95 2.2349
5
2.2317
5
2.2317
5
2.2160
5
2.2071
5
2.2072
5
2.3379
5
2.2033
5
2.2033
5
2.2014
5
  2.2004
2
2.2122
5
2.2029
5
2.2231
2
2.2139
5
2.2663
3
2.2306
2
   
B3LYP 2.2270
5
2.2097
5
2.2097
5
2.2033
5
2.1925
5
2.1925
5
2.1928
5
2.1839
5
2.1839
5
2.2854
5
2.4807
1
2.1493
5
2.2953
5
2.1823
5
2.2233
4
2.2426
4
2.2789
5
2.2771
5
   
B3LYPultrafine         2.1926
5
            2.1842
2
2.2614
2
2.2435
2
  2.2586
2
2.2340
4
     
B3PW91 2.2952
4
2.2171
5
2.2171
5
2.2077
5
2.1988
5
2.1988
5
2.1997
5
2.1939
5
2.1940
5
2.2924
5
  2.1811
2
2.2029
5
2.1916
5
  2.0228
1
       
mPW1PW91 2.2250
5
2.2220
5
2.3371
5
2.2111
5
2.2017
5
2.2017
5
2.2026
5
2.1985
5
2.1986
5
2.2445
4
  2.1845
2
2.2523
4
2.2422
4
  2.1873
3
2.2582
2
     
M06-2X 2.3300
2
2.4605
2
2.4605
2
2.4073
2
2.2517
5
2.3872
2
2.3815
2
2.3771
2
2.3771
2
2.3697
2
  2.2427
2
2.3935
2
2.3782
2
  2.3856
2
2.3754
2
     
PBEPBE 2.2884
4
2.3116
5
2.2714
4
2.2673
4
2.2984
5
2.2984
5
2.2945
5
2.2881
5
2.2040
5
2.2938
5
2.4272
1
2.2404
2
2.2141
5
2.2840
5
2.2062
2
2.2998
2
2.2860
2
2.2098
2
   
PBEPBEultrafine         2.3525
3
            2.2402
2
2.3022
2
2.2864
2
  2.2997
2
2.2858
2
     
PBE1PBE 2.2566
2
2.3007
2
2.3007
2
2.2801
2
2.2003
5
2.2669
2
2.2626
2
2.2604
2
2.2604
2
2.2605
2
  2.1856
2
2.2680
2
2.2559
2
  2.2671
2
2.2555
2
     
HSEh1PBE 2.2556
2
2.2960
2
2.2960
2
2.2763
2
2.1988
5
2.2636
2
2.2597
2
2.2566
2
2.2566
2
2.2573
2
  2.1843
2
2.2648
2
2.2522
2
  2.2639
2
2.2523
2
     
TPSSh   2.3078
2
2.3078
2
2.2749
2
2.0941
4
2.2591
2
2.0947
4
2.2554
2
      2.1814
2
2.2606
2
2.0939
4
  2.2603
2
2.2472
2
     
Moller Plesset perturbation MP2 2.6169
4
2.5206
5
2.5206
5
2.5075
5
2.4344
5
2.4344
5
2.5114
5
2.4752
5
2.5212
5
2.2004
5
  2.2034
5
2.5635
5
2.2593
5
2.2970
4
2.5071
5
2.2604
5
2.2999
4
2.0367
1
2.0170
1
MP2=FULL 2.6157
4
2.5173
5
2.6921
4
2.6750
4
2.4253
5
2.4253
5
2.4993
5
2.2411
5
2.2871
5
2.2620
4
  2.2741
2
2.5549
5
2.1667
5
2.2535
4
2.7199
3
2.1626
4
2.2537
4
2.0316
1
2.0091
1
ROMP2 2.3050
2
2.1568
2
2.1568
2
2.1521
2
2.1126
2
2.1126
2
2.1321
2
2.1342
2
2.1342
2
2.1193
2
  2.0460
1
2.1488
2
2.1289
2
2.2109
1
3.3449
2
3.9368
1
4.2233
1
   
MP3         2.4874
5
  2.0822
4
        2.2639
2
2.3985
2
2.3399
2
           
MP3=FULL         2.0808
4
  2.3051
4
        2.2617
2
2.3826
2
2.1967
2
           
MP4   2.7355
4
    2.1600
5
    1.8031
1
2.2732
4
    2.2568
2
2.3361
2
2.2553
4
  2.3420
2
2.2924
2
     
MP4=FULL   3.2148
2
    2.2932
2
      2.3130
2
      2.3252
2
2.1775
2
  2.3298
2
2.1816
2
     
B2PLYP 2.4342
1
3.1629
1
3.1629
1
2.7096
1
2.2500
4
2.5589
1
2.5383
1
2.5494
1
2.5494
1
2.5278
1
  2.3857
1
2.5666
1
2.3388
3
  2.5585
1
2.5284
1
     
B2PLYP=FULL 2.4338
1
3.1705
1
3.1705
1
2.7111
1
2.5558
1
2.5558
1
2.5355
1
2.5462
1
2.5462
1
2.5157
1
  2.3851
1
2.5630
1
2.4776
1
  2.5547
1
2.4722
1
     
Configuration interaction CID   2.7995
4
2.7995
4
2.7993
4
2.5372
5
    2.6144
5
                       
CISD   2.7950
4
2.7950
4
2.7969
4
2.5403
5
    2.8405
4
                       
Quadratic configuration interaction QCISD   2.6339
5
2.8335
4
2.8399
4
2.5798
5
2.7747
4
2.7124
5
2.6867
5
2.9076
4
2.2940
4
  3.4565
2
2.8887
4
2.8967
4
  3.3635
2
3.2748
2
     
QCISD(T)         2.2611
4
            2.2934
2
2.2883
4
2.2528
4
  2.3005
4
2.2578
4
     
QCISD(TQ)         2.5344
1
                2.4888
1
    2.4867
1
2.4632
1
   
QCISD(TQ)=FULL                           2.3230
1
2.4073
1
  2.3268
1
2.3992
1
   
Coupled Cluster CCD   2.8501
4
2.8501
4
2.8503
4
2.5832
5
2.7812
4
2.8988
4
2.6694
5
2.8881
4
2.6494
4
  3.4417
2
2.8704
4
2.7716
4
  2.8002
4
2.7300
4
     
CCSD         2.7510
4
    1.8014
1
      3.4533
2
3.5075
2
3.3795
2
3.2836
2
3.3573
2
3.2697
2
3.2502
2
   
CCSD=FULL         3.4658
2
            3.4485
2
3.4823
2
2.2070
2
2.3082
2
3.3167
2
2.2071
2
2.3018
2
   
CCSD(T)         2.6776
4
1.8056
1
  1.8095
1
    2.0282
1
2.3016
2
2.2454
5
2.2106
5
2.2400
4
2.2553
5
2.2142
5
2.2459
4
2.0462
1
2.0240
1
CCSD(T)=FULL         2.2178
4
            2.2946
2
2.2344
3
2.1159
3
2.2061
4
2.2359
3
2.1209
3
2.2085
4
2.0416
1
2.0180
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 3.2093
5
3.1961
5
3.1845
5
3.1562
5
3.1784
5
3.1458
5
density functional B1B95 2.5947
1
         
B3LYP 2.2848
5
2.2722
5
2.2888
5
2.2213
5
2.2177
5
2.1934
5
Moller Plesset perturbation MP2 2.7562
5
2.6077
5
2.6945
5
2.3009
5
2.6795
5
2.6418
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.