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Geometry Comparison

KCl (Potassium Chloride)


distance is atom 1 (K) to atom 2 (Cl)

Experimental bond length is 2.667  Å

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Calculated bond length in Å
Methods with predefined basis sets
semi-empirical PM6 2.750
composite G2 2.771
G3B3 2.675
G4 2.676

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
hartree fock HF   2.829 2.787 2.845 2.771 2.771 2.787 2.754 2.754 2.743 2.746 2.831    
density functional LSDA 2.631 2.731 2.681 2.758 2.667 2.667 2.683 2.613 2.613 2.622        
BLYP   2.813 2.759 2.836 2.753 2.748 2.769 2.705 2.705 2.707        
B1B95         2.717                  
B3LYP   2.795 2.746 2.817 2.732 2.732 2.751 2.696 2.696 2.694   2.807    
B3LYPultrafine         2.730                  
B3PW91   2.790 2.744 2.810 2.724 2.724 2.740 2.684 2.684 2.685        
mPW1PW91   2.783 2.738   2.719 2.719 2.735 2.680 2.680 2.680        
M06-2X     2.719   2.705           2.682      
PBEPBE   2.793 2.742 2.816 2.727 2.727 2.745 2.678 2.678 2.685        
PBEPBEultrafine         2.726                  
PBE1PBE         2.716                  
HSEh1PBE         2.716   2.732              
TPSSh         2.731   2.745     2.688        
wB97X-D     2.758   2.737   2.754   2.702     2.809 2.754  
B97D3   2.810     2.753   2.768   2.706   2.697     dnf
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
Moller Plesset perturbation MP2   2.874 2.876 2.862 2.750 2.741 2.762 2.700 2.698 2.691   2.892    
MP2=FULL   2.844 2.783 2.861 2.750 2.741 2.761 2.695 2.695 2.689        
MP3         2.741   2.751              
MP3=FULL         2.751   2.768              
MP4   2.882     2.742                  
B2PLYP         2.731                  
Configuration interaction CID   2.877 2.883 2.861 2.744     2.710            
CISD   2.879 2.884 2.862 2.744     2.710            
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
Quadratic configuration interaction QCISD   2.882 2.890 2.865 2.743 2.743 2.763 2.706            
QCISD(T)         2.743                  
Coupled Cluster CCD   2.880 2.889 2.863 2.752 2.743 2.762 2.705            
CCSD         2.743                  
CCSD(T)         2.743                  
CCSD(T)=FULL         2.743                  
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

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 2.885   2.891   2.813 2.812     2.756
density functional B1B95 2.882                
B3LYP 2.884   2.886   2.790 2.790     2.705
PBEPBE                 2.690
Moller Plesset perturbation MP2 2.896   2.903   2.821 2.821     2.825
Values that are outliers may reflect incorrect atom numbering for different levels of theory.
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