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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) 6-311+G(3df,2p) TZVP Def2TZVPP 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 11.954 12.010 11.946 11.887 11.935 11.946 11.898 11.940 11.945 11.935
density functional BLYP 11.873 13.608 13.608 13.234 13.086 13.087 13.262 13.243 13.248 13.079       13.116 13.258   13.261     13.258
B1B95 12.296 13.541 13.540 13.487 13.280 13.388 13.443 13.532 13.463 13.316   13.440   13.346 13.388   13.358     13.331
B3LYP 12.164 13.479 13.479 13.424 13.290 13.291 13.428 13.456 13.461 13.277 13.486 13.505 13.471 13.311 13.458 13.481 13.416 13.477 13.485 13.458
B3LYPultrafine         13.290             13.505   13.311 13.458   13.417 13.477    
B3PW91 12.259 13.566 13.566 13.474 13.327 13.327 13.424 13.455 13.458 13.302   13.488   13.335 13.439   13.396 13.453   13.439
mPW1PW91 12.225 13.504 13.527 13.429 13.257 13.256 13.358 13.378 13.402 13.251   13.442   13.265 13.366   13.348 13.403   13.366
M06-2X 12.317 13.647 13.647 13.586 13.375 13.371 13.469 13.520 13.522 13.366   13.540   13.388 13.512   13.451 13.524    
PBEPBE 12.835 13.759 13.759 13.829 13.220 13.222 13.359 13.378 13.381 13.204       13.244 13.384         13.381
PBE1PBE 12.187       13.259 13.259 13.360 13.379 13.382 13.233   13.423   13.270 13.370   13.333 13.386    
HSEh1PBE 12.166       13.244 13.243   13.369 13.372 13.217   13.412   13.253 13.361   13.319 13.376    
TPSSh         13.164 13.163 13.266 13.284   13.136   13.329   13.167 13.281   13.233 13.299    
wB97X-D     13.603   13.302   13.398   13.426     13.450   13.398 13.390     13.404    
B97D3                                   13.297    
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 Def2TZVPP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(T+d)Z
Moller Plesset perturbation MP2       13.444 13.622 13.650 13.763 13.758 13.788 13.803   13.798 13.961 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   13.809   13.702 13.964 14.058 13.847 14.020 14.084 13.964
MP3         13.094   13.067         13.242   13.161 13.397          
MP3=FULL         13.102   13.221         13.253   13.167 13.425          
MP4         13.359       13.547     13.560   13.422 13.724   13.566 13.777    
MP4=FULL         13.369       13.575         13.429 13.751   13.575 13.803    
B2PLYP         13.270         13.326         13.487     13.518    
Configuration interaction CID   13.055 13.055 13.134 12.951     13.065                        
CISD   12.971 12.971 12.955 12.910     13.031                        
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 Def2TZVPP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(T+d)Z
Quadratic configuration interaction QCISD   13.073 13.073 13.030 13.029 13.056 13.150 13.164 13.190 13.241   13.208   13.078 13.363   13.201 13.409   13.363
QCISD(T)         13.162     13.303       13.335   13.222 13.574   13.411 13.627   13.574
Coupled Cluster CCD         13.145 13.169 13.261 13.263 13.289 13.315   13.298   13.200 13.425   13.320 13.470    
CCSD         12.998 13.015 13.105 13.122   13.193   13.168   13.033 13.313 13.404 13.146 13.358 13.421  
CCSD=FULL         13.005         13.225   13.180   13.042 13.353 13.442 13.160 13.405 13.459  
CCSD(T)         13.072 13.097 13.195 13.213 13.239     13.261   13.120 13.440 13.533 13.259 13.485 13.562 13.433
CCSD(T)=FULL         13.085             13.269   13.129 13.480 13.578 13.268 13.530 13.588  
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 Def2TZVPP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pV(T+d)Z

Ionization Energies in eV
Methods with effective core potentials (select basis sets)
daug-cc-pVDZ daug-cc-pVTZ daug-cc-pVQZ Sadlej_pVTZ 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         13.303 13.112 13.358 13.218 13.491 13.471
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.