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Geometry Comparison

CH3CH(NH2)COOH (Alanine)


distance is atom 2 (C) to atom 3 (C)

Experimental bond length is 1.509  Å

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Calculated bond length in Å
Methods with predefined basis sets
semi-empirical AM1 1.527
PM3 1.522
composite G2 1.526
G3 1.526
G3B3 1.530
G4 1.532
CBS-Q 1.528

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 daug-cc-pVTZ
hartree fock HF   1.531 1.531 1.530 1.526 1.526 1.527 1.525 1.525 1.526 1.524 1.524 1.524 1.523 1.526   1.524
density functional BLYP   1.543 1.543 1.545 1.545 1.540 1.543 1.539 1.540 1.540     1.539 1.538 1.542    
B1B95   1.524 1.524 1.525 1.520 1.520 1.522 1.518 1.519 1.520     1.518 1.517 1.520    
B3LYP   1.533 1.533 1.534 1.530 1.529 1.531 1.528 1.529 1.529   1.529 1.528 1.526 1.530 1.525  
B3LYPultrafine         1.530                 1.528   1.528  
B3PW91   1.527 1.527 1.529 1.525 1.524 1.526 1.522 1.523 1.524     1.523 1.521 1.525    
mPW1PW91   1.525 1.525 1.526 1.522 1.522 1.523 1.520 1.520 1.522     1.520 1.518 1.522    
M06-2X     1.530   1.525                        
PBEPBE   1.533 1.533 1.534 1.530 1.530 1.532 1.528 1.529 0.975 0.974   1.528 1.527 1.531    
PBEPBEultrafine         1.535                        
PBE1PBE         1.521                        
HSEh1PBE   1.526         1.524             1.519      
TPSSh         1.533   1.533     1.529       1.528      
wB97X-D     1.528   1.526   1.526   1.524     1.522 1.526 1.521   1.521  
B97D3   1.536     1.534   1.534   1.532   1.529 1.529   1.529   1.529  
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 daug-cc-pVTZ
Moller Plesset perturbation MP2   1.539 1.539 1.543 1.521 1.521 1.524 1.522 1.524 1.522   1.521 1.526 1.519 1.531    
MP2=FULL   1.539 1.539 1.542 1.521 1.520 1.522 1.521 1.522 1.517     1.525 1.513      
MP3         1.525   1.525                    
MP3=FULL         1.525   1.524                    
B2PLYP         1.528                 1.521      
B2PLYP=FULLultrafine         1.528                        
Configuration interaction CID   1.535 1.535 1.537 1.520     1.520 1.521                
CISD   1.536 1.536 1.537 1.520     1.520 1.521                
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 daug-cc-pVTZ
Quadratic configuration interaction QCISD   1.544     1.526               1.531        
Coupled Cluster CCD   1.543     1.526               1.530        
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 daug-cc-pVTZ

Calculated bond length in 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 1.547   1.543   1.539 1.539     1.522
density functional B1B95 1.544 1.537              
B3LYP 1.554   1.550   1.542 1.543     1.526
PBEPBE                 1.529
Moller Plesset perturbation MP2 1.568   1.561   1.560 1.560     1.518
Values that are outliers may reflect incorrect atom numbering for different levels of theory.
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