National Institute of Standards and Technology
Computational Chemistry Comparison and Benchmark DataBase
Release 19April 2018
NIST Standard Reference Database 101
IIntroduction
IIExperimental data
IIICalculated data
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XIII Vibrations
XIVReaction data
XVEntropy data
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XVIIIon data
XVIIIBad calculations
XIXIndex of properties
XXH-bond dimers
XXIOddities

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XVII.C.1. (III.D.6.)

Calculated Ionization Energy for CH4 (Methane)

Experimental Ionization Energy is 12.61 ± 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
composite G2 12.469
G3 12.442
CBS-Q 12.465

Ionization Energies in eV
Methods with standard basis sets
3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) TZVP Def2TZVPP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ
hartree fock HF 11.953 11.953 11.892 11.777 11.589 11.589 11.696 11.517 11.513 11.525 11.486 11.475 11.485 11.487 11.450 11.481 11.486
density functional B3LYP       12.584                 12.503        
M06-2X   12.765                              
TPSSh           12.429     12.333       12.369        
wB97X-D                               12.450  
B97D3                               12.350  
3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) TZVP Def2TZVPP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ
Moller Plesset perturbation MP2 12.437 12.437 12.397 12.399 12.386 12.408 12.422 12.416 12.442 12.409 12.550 12.331 12.545 12.601 12.394 12.566 12.610
MP2=FULL 12.438 12.438 12.399 12.404 12.395 12.417 12.428 12.423 12.468     12.339 12.566 12.621     12.629
MP3       12.368   12.419                      
MP3=FULL       12.373   12.403                      
MP4 12.462     12.407       12.440                  
B2PLYP                         12.480        
Configuration interaction CID 12.405 12.405 12.357 12.318     12.322                    
CISD 12.397 12.397 12.352 12.323     12.328                    
3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) TZVP Def2TZVPP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ
Quadratic configuration interaction QCISD 12.443 12.443 12.402 12.385 12.381 12.398 12.400 12.400 12.432     12.321 12.509        
QCISD(T)       12.396               12.340 12.546   12.412 12.568  
Coupled Cluster CCD 12.451 12.451 12.407 12.378 12.379 12.394 12.392 12.399 12.428     12.322 12.508   12.381 12.526  
CCSD(T)                       12.339 12.545   12.411 12.567  
CCSD(T)=FULL       -2.776               12.347 12.568   12.419 12.591  
3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) TZVP Def2TZVPP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ

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         11.781 11.644 11.814 11.692 11.887 11.890
Moller Plesset perturbation MP2         12.251 12.255 12.324 12.359 12.380 12.383
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.