return to home page

XVII.C.1.

Calculated Ionization Energy for HCN (Hydrogen cyanide)

Experimental Ionization Energy is 13.6 ± 0.01 eV
Please note! These calculated ionizataion energies have the vibrational zero-point energy (zpe) included, but the zpe has NOT been scaled. Click on an entry for more details, including the ionization energy with a scaled zpe.
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 AM1  
PM3  
PM6  
composite G2 13.580
G3 13.579
G3B3 13.567
G4 13.555
CBS-Q 13.598

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-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(T+d)Z
hartree fock HF 10.801 12.242 12.242 12.120 11.898 11.892 11.958 11.979 11.980 11.845 12.010 11.887 11.935 11.946 11.898 11.940 11.945 11.935
density functional SVWN   14.495         14.251                      
BLYP 11.873 13.608 13.608 13.217 13.085 13.087 13.262 13.242 13.247 13.079   13.116 13.258         13.258
B1B95 12.253 13.472 13.471 13.413 13.222 13.279 13.386 13.472 13.404 13.264   13.291 13.331   13.304     13.331
B3LYP 12.164 13.474 13.474 13.424 13.290 13.291 13.428 13.456 13.461 13.277 13.505 13.311 13.458 13.481 13.416 13.477 13.485 13.458
B3LYPultrafine         13.290                     13.477    
B3PW91 12.259 13.556 13.556 13.473 13.327 13.327 13.424 13.455 13.458 13.302   13.335 13.439         13.439
mPW1PW91 12.225 13.498 13.521 13.429 13.257 13.256 13.358 13.378 13.402 13.251   13.265 13.366         13.366
M06-2X         13.375                          
PBEPBE 12.835 13.759 13.759 13.389 13.220 13.221 13.358 13.375 13.378 13.204   13.243 13.381         13.381
PBE1PBE         13.259                          
HSEh1PBE         13.645                          
TPSSh         13.164   13.266                      
Moller Plesset perturbation MP2 12.324     13.444 13.622 13.650 13.763 13.758 13.788 13.803 13.798 13.696 13.942 14.035 13.841 13.997 14.062 13.942
MP2=FULL         13.630 13.659 13.772 13.770 13.799 13.817   13.702 13.964 14.057     14.084 13.964
MP3         13.094   13.121                      
MP3=FULL         13.102   13.221                      
MP4         13.358       13.546       14.207          
Configuration interaction CID   13.055 13.055 13.128 12.951     13.065                    
CISD   12.962 12.962 12.945 12.910     13.030                    
Quadratic configuration interaction QCISD   13.073 13.073 13.030 13.034 13.056 13.150 13.164 13.189 13.241   13.078 13.363         13.363
QCISD(T)         13.162             13.222 13.574   13.412 13.635   13.574
Coupled Cluster CCD   13.256 13.256 13.332 13.145 13.169 13.261 13.263 13.289 13.312   13.200 13.425   13.320 13.470    
CCSD(T)         13.072             13.120 13.433 13.532 13.254 13.485 13.551 13.433
CCSD(T)=FULL         13.085                 13.568        

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 12.026 11.780 12.057 11.906 12.110 12.108
density functional B3LYP 13.302 13.112 13.358 13.218 13.490 13.470
Moller Plesset perturbation MP2   13.571   13.653    
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.