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 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
semi-empirical AM1  
PM3  
composite G2 12.469
G3 12.442
G3B3 12.378
G4 12.392
CBS-Q 12.465

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
hartree fock HF 11.416 11.953 11.953 11.892 11.777 11.589 11.589 11.696 11.517 11.513 11.525 11.475 11.485 11.487 11.450 11.481 11.486
density functional LSDA 12.533 13.135 13.135 13.106 13.022 12.916 12.979 13.087 12.968 12.867   12.842 12.951 12.959 12.885 12.951 12.959
SVWN   13.135     13.022   12.979       12.972            
BLYP 11.947 12.432 12.432 12.401 12.317 12.218 12.304 12.410 12.306 12.173   12.161 12.297        
B1B95 12.229 12.647 12.647 12.598 12.514 12.244 12.436 12.524 12.403 12.347   12.313 12.387 12.394   12.387 12.393
B3LYP 12.240 12.717 12.717 12.674 12.584 12.471 12.529 12.631 12.515 12.419 12.524 12.395 12.503 12.509 12.438 12.502 12.508
B3LYPultrafine         12.584                     12.502  
B3PW91 12.279 12.738 12.738 12.678 12.576 12.449 12.484 12.580 12.450 12.390   12.357 12.429        
mPW1PW91 12.260 12.720 12.720 12.658 12.552 12.420 12.457 12.551 12.417 12.359   12.330 12.397        
M06-2X     12.644   12.644                        
PBEPBE 12.053 12.547 12.547 12.504 12.405 12.286 12.353 12.452 12.328 12.233   12.220 12.313 12.319     12.319
PBE1PBE         12.516                        
HSEh1PBE   13.598     13.492   13.418           13.350        
TPSSh         12.495   12.429     12.333     12.369        
wB97X-D     12.762   12.601       12.477       12.448     12.450  
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
Moller Plesset perturbation MP2 11.626 12.437 12.437 12.397 12.399 12.386 12.408 12.423 12.416 12.442 12.409 12.331 12.545 12.601 12.394 12.566 12.610
MP2=FULL 11.627 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     12.406       12.440                
B2PLYP         12.488               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                  
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
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         12.285             12.347 12.568   12.419 12.591  
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

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 11.781 11.644 11.814 11.692 11.887 11.890
density functional B3LYP 12.517 12.414 12.615 12.525 12.661 12.658
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.