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Comparison of levels of theory for C-I


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 2.0517
15
PM3 1.9819
16
PM6 2.1498
18

average calculated bond lengths (Å)
Methods with standard basis sets
STO-3G 3-21G 3-21G* 6-31G* 6-311G* 6-311G**
hartree fock HF 2.1429
19
2.1807
19
2.1689
19
  2.1427
8
2.1551
5
ROHF   2.0323
1
2.0281
1
     
density functional LSDA 1.9802
1
1.9982
1
1.9982
1
  2.1290
7
2.1468
4
BLYP 2.2092
19
2.2408
19
2.2182
19
  2.1972
8
2.2131
5
B1B95 2.1617
19
2.1625
19
2.1606
19
  2.1365
8
2.1504
5
B3LYP 2.1819
19
2.2098
19
2.1899
19
  2.1662
8
2.1806
5
B3LYPultrafine   2.2096
18
    2.1615
6
2.1822
4
B3PW91 2.1737
19
2.1922
19
2.1731
19
  2.1492
8
2.1634
5
mPW1PW91 2.1664
19
2.1848
19
2.1664
19
  2.1426
8
2.1564
5
M06-2X 2.1524
19
2.1775
18
2.1608
20
  2.1372
7
2.1521
4
PBEPBE 2.1909
19
2.2109
19
2.1888
19
  2.1673
8
2.1819
5
PBEPBEultrafine   2.2110
18
    2.1619
6
2.1849
4
PBE1PBE 2.1644
19
2.1655
18
2.1645
18
  2.1395
7
2.1559
4
HSEh1PBE 2.1666
19
2.1870
18
2.1681
18
  2.1399
6
2.1602
4
TPSSh 2.1828
19
2.2005
18
2.1800
18
  2.1527
6
2.1743
4
wB97X-D 2.1625
19
2.1805
18
2.1656
20
  2.1360
6
2.1556
4
B97D3 2.2062
19
2.2271
20
2.2024
18
  2.1750
6
2.1986
4
STO-3G 3-21G 3-21G* 6-31G* 6-311G* 6-311G**
Moller Plesset perturbation MP2 2.1740
19
2.2059
19
2.1929
19
2.1756
2
2.1427
8
2.1534
5
MP2=FULL 2.1739
19
2.2045
19
2.1915
19
  2.1435
8
2.1541
5
ROMP2 2.0244
1
  2.0452
1
  2.1642
1
 
MP3         2.1421
6
2.1586
4
MP3=FULL   2.1980
10
2.1807
9
  2.1427
6
2.1591
4
MP4   2.2162
10
    2.1525
6
2.1696
4
MP4=FULL   2.2149
10
    2.1472
5
2.1708
4
B2PLYP 2.1747
19
2.2051
18
2.1883
18
  2.1518
6
2.1709
4
B2PLYP=FULL 2.1747
19
2.2047
18
2.1878
18
  2.1519
6
2.1711
4
B2PLYP=FULLultrafine 2.1747
19
2.2047
18
2.1878
18
  2.1519
6
2.1711
4
Configuration interaction CID   2.1955
19
2.1803
19
  2.1351
8
2.1455
5
CISD   2.1975
19
2.1812
19
  2.1363
8
2.1470
5
STO-3G 3-21G 3-21G* 6-31G* 6-311G* 6-311G**
Quadratic configuration interaction QCISD   2.2110
19
2.1979
19
  2.1516
8
2.1615
5
QCISD(T)   2.2222
1
2.2127
1
  2.1560
7
2.1685
5
QCISD(T)=FULL         2.1535
6
2.1709
4
Coupled Cluster CCD   2.2062
19
2.1948
19
  2.1469
8
2.1565
5
CCSD         2.1456
6
2.1611
4
CCSD=FULL         2.1458
6
2.1613
4
CCSD(T)   2.2218
1
2.2124
1
  2.1549
7
2.1678
5
CCSD(T)=FULL         2.1528
6
2.1697
4
STO-3G 3-21G 3-21G* 6-31G* 6-311G* 6-311G**

average calculated bond lengths (Å)
Methods with effective core potentials (select basis sets)
CEP-31G CEP-31G* CEP-121G CEP-121G* LANL2DZ SDD cc-pVTZ-PP aug-cc-pVTZ-PP Def2TZVPP
hartree fock HF 2.1646
20
  2.1643
21
  2.1643
21
2.1695
21
2.1413
20
  2.1349
21
ROHF             2.1390
2
  2.0976
3
density functional LSDA             2.1298
20
  2.0648
3
BLYP             2.2002
20
  2.1924
20
B1B95 2.1765
1
  2.1717
1
  2.1769
1
2.1832
1
2.1382
20
  2.1312
20
B3LYP 2.1950
20
  2.1953
21
  2.1862
21
2.1941
21
2.1688
20
  2.1625
21
B3LYPultrafine             2.1688
20
  2.1613
20
B3PW91             2.1505
20
  2.1435
20
mPW1PW91             2.1434
20
  2.1365
20
M06-2X             2.1392
20
  2.1334
20
PBEPBE             2.1684
20
  2.1626
21
PBEPBEultrafine             2.1684
20
  2.1610
20
PBE1PBE             2.1412
20
  2.1343
20
HSEh1PBE             2.1457
20
  2.1385
20
TPSSh             2.1586
20
  2.1514
20
wB97X-D 2.1715
18
  2.1715
19
  2.1649
19
2.1690
19
2.1428
20
  2.1359
20
B97D3             2.1853
20
  2.1776
20
Moller Plesset perturbation MP2 2.1935
20
  2.1924
21
  2.1903
21
2.1958
21
2.1302
20
  2.1194
21
MP2=FULL             2.1265
20
  2.1121
20
ROMP2             2.1244
1
  2.0720
3
MP3             2.1353
20
  2.1180
12
MP3=FULL             2.1310
19
  2.1121
12
MP4             2.1451
20
  2.1246
12
MP4=FULL             2.1415
20
  2.1178
12
B2PLYP             2.1536
20
  2.1451
20
B2PLYP=FULL             2.1525
20
  2.1432
20
B2PLYP=FULLultrafine             2.1525
20
  2.1432
20
Configuration interaction CID             2.1233
20
  2.1126
20
CISD             2.1239
20
  2.1131
20
Quadratic configuration interaction QCISD             2.1373
20
  2.1285
20
QCISD(T)             2.1437
20
  2.1354
20
QCISD(T)=FULL             2.1392
19
  2.1274
18
QCISD(TQ)                 1.9928
1
Coupled Cluster CCD             2.1346
20
  2.1256
20
CCSD             2.1364
20
  2.1277
20
CCSD=FULL             2.1328
20
  2.1213
20
CCSD(T)             2.1432
20
  2.1341
19
CCSD(T)=FULL             2.1396
20
  2.1282
20
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.