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III.G.1.a.

Comparison of levels of theory for P-P


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 1.6994
2
PM3 2.0690
10
PM6 2.1266
10
composite G2 2.1006
10
G3 2.1006
10
G3B3 2.1459
10
CBS-Q 2.1006
10
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-pV(D+d)Z cc-pV(T+d)Z cc-pCVDZ cc-pCVTZ
hartree fock HF 2.0722
10		 2.2845
10		 2.0905
10		 2.2490
10		 2.0932
10		 2.1006
10		 2.1013
10		 2.1012
10		 2.1013
10		 2.1023
10		 2.1382
8		 2.1125
10		 2.1219
10		 2.1051
10		 2.1000
10		 2.1246
10		 2.1051
10		 1.9858
4		 1.8571
1		 2.1384
8		 1.8654
1		 1.8519
1
ROHF         1.9562
1		                                  
density functional LSDA 2.1253
10		 2.2800
10		 2.1140
10		 2.2726
10		 2.1320
10		 2.1320
10		 2.1317
10		 2.1283
10		 2.1283
10		 2.1224
10		     2.1476
10		 2.1244
10		 1.9786
2		 2.1483
10		 1.9814
2		 1.9761
2		 1.8980
1		 1.8878
1		    
SVWN   2.3015
10		     2.1657
8		   2.1318
10		                              
BLYP 2.1564
10		 2.3480
10		 2.1577
10		 2.3215
10		 2.1761
10		 2.1761
10		 2.1761
10		 2.1755
10		 2.1756
10		 2.1656
10		     2.1898
10		 2.1678
10		   2.2309
8		     1.9205
1		 1.9113
1		    
B1B95 2.1124
10		 2.2730
10		 2.1043
10		 2.2617
10		 2.1162
10		 2.1187
10		 2.1187
10		 2.1188
10		 2.1188
10		 2.1150
10		     2.1361
10		 2.1150
10		 1.9666
2		 2.1354
10		 1.9693
2		 1.9645
2		 1.8842
1		 1.8766
1		    
B3LYP 2.1300
10		 2.3185
10		 2.1285
10		 2.2898
10		 2.1459
10		 2.1455
10		 2.1455
10		 2.1443
10		 1.9913
2		 2.1377
10		 2.1686
8		 2.1508
10		 2.1608
10		 2.1399
10		 2.0226
4		 2.1618
10		 2.1397
10		 2.0215
4		 1.8971
1		 2.1685
8		    
B3LYPultrafine         2.1459
10		                                  
B3PW91 1.9635
2		 2.3064
10		 2.1165
10		 2.2739
10		 2.1310
10		 2.1310
10		 2.1311
10		 2.1299
10		 1.9819
2		 2.1254
10		     2.1477
10		 2.1277
10		   2.1879
8		     1.8924
1		 1.8842
1		    
mPW1PW91 1.9569
2		 2.3000
10		 1.9715
2		 2.2670
10		 2.1246
10		 2.1247
10		 2.1248
10		 2.1239
10		 2.1240
10		 2.1198
10		     2.1417
10		 2.1223
10		   2.1821
8		     1.8877
1		 1.8799
1		    
M06-2X         2.1157
10		                           1.8793
1		 1.8724
1		    
PBEPBE 1.9851
2		 2.3274
10		 1.9996
2		 2.1093
2		 2.1521
10		 2.1521
10		 2.1521
10		 2.1520
10		 2.1520
10		 2.1446
10		 2.1738
8		   2.0566
4		 2.1472
10		 1.9970
2		   2.1837
8		 1.9943
2		 1.9129
1		 1.9044
1		    
PBEPBEultrafine         2.1867
8		                                  
HSEh1PBE         2.1408
9		                           1.8894
1		 1.8818
1		    
Moller Plesset perturbation MP2FC 2.0331
2		 2.4014
10		 2.1171
10		 2.3637
10		 2.1354
10		 2.1354
10		 2.1360
10		 2.1366
10		 2.1367
10		 2.1383
10		   2.1509
10		 2.1670
10		 2.1410
10		 2.1211
9		 2.1759
10		 2.0373
4		 1.9657
3		 1.9342
1		 2.1666
8		 2.1922
7		 1.9194
1
MP2FU 2.0326
2		 2.4029
10		 1.9927
2		 2.1890
2		 2.1327
10		 2.1327
10		 2.1335
10		 2.1358
10		 2.0021
2		 1.9934
2		     2.1648
10		 2.1227
9		 2.1158
9		 2.2053
7		 1.9191
1		 1.9854
2		 1.9310
1		 2.1527
8		 2.1894
7		 1.9136
1
MP3         2.1301
10		                           1.9017
1		 1.8887
1		    
MP4   2.1713
2		     2.1443
10		     2.0801
2		 2.0077
2		         2.0583
3		         1.9354
1		 1.9222
1		    
B2PLYP         2.1409
10		   2.1413
10		                       1.9118
1		 1.9020
1		    
Configuration interaction CID   2.1106
2		 1.9645
2		 2.1037
2		 2.1162
10		     2.0113
4		                            
CISD   2.1151
2		 1.9674
2		 2.1072
2		 2.1178
10		     1.9726
2		                            
Quadratic configuration interaction QCISD   2.3706
10		 1.9808
2		 2.1311
2		 2.1336
10		 1.9952
2		 2.0312
4		 2.1345
10		 2.1232
9		 1.9867
2		     2.0475
4		 1.9855
2		         1.9114
1		 1.8955
1		    
QCISD(T)         2.0419
4		     2.0772
2		         2.0261
2		 2.0022
2		   2.0290
2		 2.0012
2		   1.9261
1		 1.9110
1		    
Coupled Cluster CCD   2.1345
2		 1.9753
2		 2.1238
2		 2.1294
10		 1.9891
2		 1.9874
2		 2.0228
4		 1.9812
2		 1.9811
2		     2.0462
4		 1.9796
2		   2.0066
2		 1.9785
2		   1.9061
1		 1.8897
1		    
CCSD         2.1483
9		     2.0676
2		                     1.9095
1		 1.8936
1		    
CCSD(T)   2.0210
1		     2.1567
9		 2.0753
2		 1.9210
1		 2.0765
2		 1.9126
1		   1.9071
1		   2.1656
9		 2.1358
9		   2.1725
9		 2.1362
9		   1.9249
1		 1.9095
1		 2.2018
7		 2.1663
7
CCSD(T)=FULL         2.1294
9		               2.2035
7		 2.1640
7		   2.2118
7		 1.9090
1		   1.9231
1		 1.9058
1		 2.1990
7		 1.9052
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 2.2487
10		 2.1324
10		 2.2516
10		 2.1289
10		 2.2748
10		 2.2739
10
density functional B1B95 2.3343
8		 2.2033
8		        
B3LYP 2.3066
10		 2.1763
10		 2.3046
10		 2.1741
10		 2.3323
10		 2.3161
10
Moller Plesset perturbation MP2FC 2.3693
10		 2.1808
10		 2.3644
10		 2.1777
10		 2.3962
10		 2.3902
10
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.