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XVII.C.1.

Calculated Ionization Energy for He (Helium atom)

Experimental Ionization Energy is 24.58741 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 24.446
G2MP2 24.543
G2 24.543
G3 24.570
G3B3 24.583
G3MP2 24.553
G4 24.586

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 cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVTZ
hartree fock HF 23.838 23.410 23.410 23.444 23.444 23.444 23.444 23.450 23.450 23.444 23.450 23.444 23.463 23.448  
density functional LSDA 24.659 24.577 24.577 24.713 24.713 24.713 24.713 24.766 24.766 24.713   24.713 24.782    
BLYP 24.891 24.563 24.563 24.710 24.710 24.710 24.710 24.791 24.791 24.710   24.710 24.809    
B1B95 24.910 24.538 24.538 24.647 24.647 24.647 24.647 24.698 24.698 24.647   24.647 24.709    
B3LYP 25.085 24.746 24.746 24.868 24.868 24.868 24.868 24.926 24.926 24.868 24.926 24.868 24.940 24.939  
B3LYPultrafine         24.868                   24.946
B3PW91 24.942 24.561 24.561 24.664 24.664 24.664 24.664 24.709 24.709 24.664   24.665 24.722    
mPW1PW91 24.834 24.413 24.421 24.530 24.522 24.522 24.522 24.570 24.578 24.530   24.522 24.585    
PBEPBE 24.587 24.236 24.236 24.382 24.382 24.382 24.382 24.449 24.449 24.382   24.383 24.464    
PBE1PBE         24.395                    
HSEh1PBE         24.413                    
TPSSh         24.693   24.693           24.742    
Moller Plesset perturbation MP2 23.838 23.723 23.723 23.749 23.749 24.137 24.728 23.801 24.121 24.137 24.176 24.146 24.364 24.414  
MP2=FULL 23.838 23.723 23.723 23.749 23.749 24.137 24.137 23.801 24.121 24.137   24.146 24.364 24.414  
MP3         23.827   24.285                
MP3=FULL         23.827   24.285                
MP4   23.811     23.846       24.278       24.521    
Configuration interaction CID   23.815 23.815 23.852 23.852     23.896              
CISD   23.815 23.815 23.852 23.852     23.899              
Quadratic configuration interaction QCISD   23.815 23.815 23.852 23.852 24.320 24.320 23.899 24.284 24.320   24.326 24.526    
QCISD(T)         23.852             24.326 24.526    
Coupled Cluster CCD   23.815 23.815 23.852 23.852 24.320 24.320 23.896 24.282 24.320   24.326 24.525    
CCSD         23.852             24.326 24.526    
CCSD(T)         23.852             24.326 24.526 24.561  
CCSD(T)=FULL         23.852             24.326 24.526 24.561  

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     23.450 23.450   23.444
density functional B3LYP     24.926 24.926   24.868
Moller Plesset perturbation MP2     23.801 23.801   23.749
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.