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IV.D.1. (XII.C.1.)

Geometry Comparison

C4H6 (Cyclobutene)


distance is atom 1 (C) to atom 3 (C)

Experimental bond length is 1.517  Å

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Calculated bond length in Å
Methods with predefined basis sets
semi-empirical PM3 1.518
PM6 1.523
composite G2 1.515
G3 1.515
G3B3 1.519
G4 1.519
CBS-Q 1.517

Calculated bond length in 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 aug-cc-pVDZ aug-cc-pVTZ
hartree fock HF 1.526 1.539 1.539 1.524 1.515 1.514 1.515 1.516 1.516 1.515 1.513 1.515 1.517 1.514 1.518 1.514
density functional LSDA 1.526 1.524 1.524 1.513 1.501 1.500 1.502 1.500 1.500 1.500     1.503 1.497 1.503  
SVWN   1.524     1.501   1.502                  
BLYP 1.555 1.553 1.553 1.540 1.529 1.529 1.531 1.529 1.529 1.529     1.531 1.526 1.532  
B1B95 1.530 1.534 1.534 1.520 1.508 1.508 1.509 1.508 1.508 1.508     1.509 1.505 1.509  
B3LYP 1.543 1.542 1.542 1.530 1.519 1.518 1.520 1.519   1.519 1.516 1.517 1.521 1.515 1.521 1.515
B3LYPultrafine         1.519   1.520             1.515   1.516
B3PW91   1.538 1.538 1.525 1.513 1.513 1.514 1.513   1.513     1.515 1.510 1.515  
mPW1PW91   1.536   1.523 1.511 1.511 1.512 1.511 1.511 1.511     1.512 1.508 1.513  
M06-2X         1.514                      
PBEPBE   1.545     1.519 1.519 1.521 1.519 1.519 1.519 1.516   1.520 1.517   1.516
PBEPBEultrafine         1.519                      
PBE1PBE         1.511                      
HSEh1PBE         1.510                      
TPSSh         1.517   1.518             1.514    
Moller Plesset perturbation MP2   1.553 1.553 1.542 1.513 1.513 1.515 1.519 1.519     1.514 1.523 1.513 1.526  
MP2=FULL   1.553     1.512 1.511 1.513 1.517         1.522 1.506    
MP3         1.519   1.518                  
MP3=FULL         1.517   1.518                  
MP4         1.521                      
B2PLYP         1.517                 1.514    
B2PLYP=FULLultrafine         1.516                      
Configuration interaction CID         1.513                      
CISD         1.514                      
Quadratic configuration interaction QCISD   1.561     1.520     1.525 1.525              
Coupled Cluster CCD         1.519                      
CCSD(T)         1.523                      

Calculated bond length in Å
Methods with effective core potentials (select basis sets)
CEP-31G CEP-31G* CEP-121G CEP-121G* LANL2DZ SDD
hartree fock HF 1.541 1.531 1.536 1.526 1.532 1.532
density functional B1B95 1.540 1.529        
B3LYP 1.551 1.539 1.545 1.533 1.538 1.538
Moller Plesset perturbation MP2 1.570 1.537 1.561 1.529 1.560 1.560
Values that are outliers may reflect incorrect atom numbering for different levels of theory.
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