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III.G.1.a.

Comparison of levels of theory for Si-C


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 1.6318
6
PM3 1.6646
7
PM6 1.7978
15
composite G2 1.8443
11
G3 1.8443
11
G3B3 1.7602
8
CBS-Q 1.8252
11
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(T+d)Z
hartree fock HF 1.7778
11		 1.8750
11		 1.8199
11		 1.8506
10		 1.8082
12		 1.8434
11		 1.8439
11		 1.8207
11		 1.8205
11		 1.8176
11		 1.8821
5		 1.8385
15		 1.8312
11		 1.8211
11		 1.7314
5		 1.8316
11		 1.8199
11		 1.7315
5		 1.8827
10
ROHF 1.6627
2		 1.7841
2		 1.7266
2		 1.7842
2		 1.7249
2		 1.7249
2		 1.7297
2		 1.7237
2		 1.7237
2		 1.7202
2		     1.7385
2		 1.7275
2		 1.7233
2		 1.7446
2		 1.7303
2		 1.7246
2		  
density functional LSDA 1.7974
11		 1.8407
11		 1.8152
11		 1.8448
11		 1.8154
11		 1.8148
11		 1.8158
11		 1.8096
11		 1.8100
11		 1.8064
11		     1.8218
11		 1.8088
11		 1.7482
2		 1.8202
11		 1.7742
5		 1.7487
2		  
SVWN   1.8418
15		     1.8233
14		   1.8116
15		                        
BLYP 1.8231
11		 1.8785
11		 1.8449
11		 1.8786
11		 1.8460
11		 1.8453
11		 1.8470
11		 1.8416
11		 1.8418
11		 1.8372
11		     1.8364
12		 1.8409
11		   1.9071
1		      
B1B95 1.7183
8		 1.7679
8		 1.7520
8		 1.7874
8		 1.7520
8		 1.7521
8		 1.8110
11		 1.7486
8		 1.7489
8		 1.7460
8		     1.7602
8		 1.7489
8		 1.6704
3		 1.7608
8		 1.7530
5		 1.6710
3		  
B3LYP 1.7947
11		 1.8518
11		 1.8185
11		 1.8509
11		 1.8198
11		 1.8191
11		 1.8205
11		 1.8154
11		 1.8088
10		 1.8118
11		 1.8771
1		 1.8303
15		 1.8253
11		 1.8152
11		 1.7218
5		 1.8256
11		 1.8152
11		 1.7222
5		 1.8834
10
B3LYPultrafine         1.8197
11		                            
B3PW91 1.7824
10		 1.8480
11		 1.8155
11		 1.8465
11		 1.8160
11		 1.8153
11		 1.8161
11		 1.8111
11		 1.8045
10		 1.8085
11		     1.8213
11		 1.8112
11		   1.8893
1		      
mPW1PW91 1.7786
10		 1.8450
11		 1.8055
10		 1.8435
11		 1.8128
11		 1.8121
11		 1.8129
11		 1.8079
11		 1.8082
11		 1.8055
11		     1.8180
11		 1.8081
11		   1.8864
1		      
M06-2X         1.8181
15		                            
PBEPBE 1.8080
10		 1.8710
11		 1.8332
10		 1.8650
10		 1.8386
11		 1.8379
11		 1.8389
11		 1.8335
11		 1.8338
11		 1.8307
11		 1.8821
1		   1.8437
11		 1.8336
11		 1.7282
3		 1.8220
3		 1.8307
4		 1.7288
3		  
PBEPBEultrafine         1.8946
3		                            
HSEh1PBE         1.8343
14		                            
Moller Plesset perturbation MP2FC 1.8281
10		 1.8655
11		 1.8286
11		 1.8659
11		 1.8260
11		 1.8250
11		 1.8233
11		 1.8209
11		 1.8206
11		 1.8124
10		   1.8268
15		 1.8363
11		 1.8089
9		 1.6745
1		 1.8401
11		 1.8012
6		   1.8767
10
MP2FU 1.8277
10		 1.8651
11		 1.8214
10		 1.8590
10		 1.8231
11		 1.8219
11		 1.8230
11		 1.8171
11		 1.8108
10		 1.8055
10		     1.8337
11		 1.8085
10		 1.6648
1		 1.7152
2		 1.7136
3		   1.8670
10
ROMP2 1.7367
3		 1.8256
3		 1.7676
3		 1.8411
3		 1.7663
3		 1.7658
3		 1.7677
3		 1.7622
3		 1.7620
3		 1.7068
2		     1.7835
3		 1.7650
3		 1.7828
2		 1.7902
3		 1.7952
2		 1.7848
2		  
MP3         1.8201
11		                            
MP4   1.8712
9		     1.8361
10		     1.8833
1		 1.8143
7		         1.6939
3		          
B2PLYP         1.8224
15		   1.8227
15		                        
Configuration interaction CID   1.8478
10		 1.8125
10		 1.8475
10		 1.8174
11		     1.8130
11		                      
CISD   1.8602
9		 1.8126
10		 1.8612
9		 1.8250
10		     1.8029
10		                      
Quadratic configuration interaction QCISD 1.8855
2		 1.8694
11		 1.8231
10		 1.8649
10		 1.8227
11		 1.8153
10		 1.8158
10		 1.8177
11		 1.8278
10		 1.8193
9		     1.7965
7		 1.7766
4		          
QCISD(T)         1.8159
9		     1.8840
1		         1.7391
3		 1.7012
3		   1.7066
2		 1.6838
2		    
Coupled Cluster CCD 1.8854
2		 1.8571
10		 1.8199
10		 1.8579
10		 1.8233
11		 1.8161
10		 1.8142
10		 1.8186
11		 1.8235
9		 1.8207
9		     1.7998
7		 1.7751
5		   1.7347
3		 1.6974
2		    
CCSD         1.8064
9		     1.8820
1		                      
CCSD(T)         1.8483
9		 1.8876
1		   1.8838
1		         1.7301
4		 1.7071
4		 1.6588
1		 1.7188
3		 1.7138
3		    
CCSD(T)=FULL         1.6997
3		                   1.6604
2		     1.6713
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 1.8524
10		 1.8471
11		 1.8526
10		 1.8534
11		 1.8332
10		 1.8368
11
density functional B1B95 1.9153
7		 1.8988
7		 1.9157
2		 1.8938
2		 1.8941
2		 1.8973
2
B3LYP 1.8560
11		 1.8324
11		 1.8571
11		 1.8315
11		 1.8397
11		 1.8426
11
Moller Plesset perturbation MP2FC 1.8718
11		 1.8417
11		 1.8683
11		 1.8350
11		 1.8579
11		 1.8587
11
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.