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Geometry Comparison

KBr (Potassium Bromide)


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

Experimental bond length is 2.821  Å

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Calculated bond length in Å
Methods with predefined basis sets
semi-empirical PM6 2.996
composite G2 2.895
G3B3 2.839
G4 2.838

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   2.998 2.881 2.967 2.894 2.895 2.930 2.912 2.912 2.892 2.913 2.992    
density functional LSDA 2.736 2.901 2.767 2.870 2.783 2.783 2.815 2.757 2.757 2.759        
BLYP   2.988 2.852 2.951 2.872 2.868 2.907 2.857 2.857 2.848        
B1B95         2.838                  
B3LYP   2.967 2.839 2.933 2.853 2.853 2.889 2.847 2.847 2.836   2.962    
B3LYPultrafine         2.853                  
B3PW91   2.963 2.835 2.927 2.844 2.844 2.877 2.834 2.834 2.827        
mPW1PW91   2.955 2.829   2.839 2.839 2.872 2.831 2.831 2.823        
M06-2X     2.828   2.834           2.842      
PBEPBE   2.966 2.833 2.931 2.846 2.846 2.881 2.829 2.829 2.826        
PBEPBEultrafine         2.846                  
PBE1PBE         2.836                  
HSEh1PBE         2.837   2.870              
TPSSh         2.848   2.881     2.829        
wB97X-D     2.847   2.853   2.889   2.852     2.955 2.889  
B97D3   2.973     2.872   2.906   2.857   2.857     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   3.016 2.908 2.979 2.875 2.868 2.906 2.855 2.853 2.836   3.013    
MP2=FULL   3.011 2.875 2.979 2.871 2.865 2.903 2.847            
MP3         2.870   2.877              
MP3=FULL         2.874   2.910              
MP4   3.021     2.869                  
B2PLYP         2.854                  
B2PLYP=FULLultrafine         2.853                  
Configuration interaction CID   3.017 2.907 2.980 2.872     2.869            
CISD   3.018 2.907 2.981 2.871     2.868            
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   3.020 2.910 2.982 2.870 2.870 2.907 2.864            
QCISD(T)         2.869                  
Coupled Cluster CCD   3.018 2.909 2.981 2.877 2.870 2.907 2.863            
CCSD         2.870                  
CCSD(T)         2.868                  
CCSD(T)=FULL         2.865                  
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 3.074   3.074   3.015 3.031     2.921
density functional B1B95 3.053                
B3LYP 3.069   3.069   2.982 2.998     2.869
PBEPBE                 2.854
Moller Plesset perturbation MP2 3.091   3.091   3.017 3.038     2.979
Values that are outliers may reflect incorrect atom numbering for different levels of theory.
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