National Institute of Standards and Technology
Computational Chemistry Comparison and Benchmark DataBase
Release 17bSeptember 2015
NIST Standard Reference Database 101
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XIXIndex of properties
XXH-bond dimers
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XVII.C.1. (III.D.6.)

Calculated Ionization Energy for K (Potassium atom)

Experimental Ionization Energy is 4.34066 ± 0.00001 eV
Original data displayed. Press to display differences.
Differences displayed. Press to display original data.

Ionization Energies in eV
Methods with predefined basis sets
semi-empirical PM6  
composite G1 4.269
G2MP2 4.279
G2 4.271
G3B3 4.307
G3MP2 4.324
G4 4.317

Ionization Energies in eV
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) TZVP
hartree fock HF 1.862 3.983 3.984 4.010 4.010 4.010 4.010 4.003 4.003 4.010 4.009
ROHF   3.982 3.983 4.008 4.008 4.008 4.008 4.001 4.001    
density functional LSDA 3.463 4.824 4.834 4.887 4.917 4.917 4.917 4.915 4.915 4.917  
SVWN                     4.907
BLYP 2.871 4.382 4.383 4.406 4.432 4.432 4.433 4.426 4.426 4.433  
B1B95     4.218 4.260 4.288 4.266 4.266 4.255 4.255 4.271  
B3LYP 2.895 4.452 4.453 4.480 4.502 4.502 4.502 4.494 4.494 4.502 4.489
B3LYPultrafine         4.502            
B3PW91 2.736 4.318 4.320 4.364 4.373 4.373 4.373 4.365 4.365 4.377  
mPW1PW91 2.675 4.322 4.324 4.353 4.360 4.360 4.360 4.351 4.351 4.365  
M06-2X     4.271                
PBEPBE 2.808 4.407 4.408 4.432 4.446 4.446 4.446 4.439 4.439 4.450  
PBE1PBE         4.377            
TPSSh         4.240   4.240     4.246  
wB97X-D     4.038   4.130       4.122    
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) TZVP
Moller Plesset perturbation HF MP2 1.862 3.983 3.984 4.015 4.124 4.124 4.126 4.234 4.234 4.157 4.009
MP2=FULL 1.896 3.989 4.020 4.015 4.124 4.124 4.126 4.237 4.237 4.157  
HF MP3             4.140        
MP3=FULL         4.140   4.142        
HF MP4   3.983     4.146       4.243    
Configuration interaction HF CID   3.983 3.984 4.017 4.141     4.198      
HF CISD   3.983 3.984 4.017 4.144     4.204      
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) TZVP
Quadratic configuration interaction HF QCISD   3.983 3.984 4.017 4.147 4.147 4.149 4.237 4.237 4.161  
HF QCISD(T)         4.148            
Coupled Cluster HF CCD   3.983 3.984 4.017 4.143 4.143 4.146 4.224 4.224 4.158  
HF CCSD         4.146            
HF CCSD(T)         4.148            
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) TZVP

Ionization Energies in eV
Methods with effective core potentials (select basis sets)
CEP-31G CEP-31G* CEP-121G CEP-121G* LANL2DZ SDD
hartree fock HF         3.985 3.996
density functional B3LYP         4.445 4.497
Moller Plesset perturbation MP2         3.990 4.030
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.