National Institute of Standards and Technology

Computational Chemistry Comparison and Benchmark DataBase
Release 22	May 2022
NIST Standard Reference Database 101

I	Introduction
II	Experimental data
III	Calculated data
IV	Data comparisons
V	Cost comparisons
VI	Input and output files
VII	Tutorials and Units
VIII	Links to other sites
IX	Feedback
X	Older CCCBDB versions
XII	Geometries
XIII	Vibrations
XIV	Reaction data
XV	Entropy data
XVI	Bibliographic data
XVII	Ion data
XVIII	Bad calculations
XIX	Index of properties
XX	H-bond dimers
XXI	Oddities

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

Calculated Ionization Energy for C₂H₄ (Ethylene)

Experimental Ionization Energy is 10.5138 ± 0.0006 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.

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Ionization Energies in eV

Methods with predefined basis sets

composite	G2	10.533
	G3	10.516
	G3MP2	10.557
	G4	10.429
	CBS-Q	10.537

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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	cc-pVDZ	cc-pVTZ	cc-pVQZ	aug-cc-pVDZ	aug-cc-pVTZ	aug-cc-pVQZ	daug-cc-pVTZ
hartree fock	HF	7.383	8.896	8.896	8.739	8.647	8.643	8.747	8.726	8.733	8.611		8.770	8.702	8.738	8.749	8.720	8.745	8.751	8.746
density functional	BLYP	8.895	10.102	10.102	10.008	9.956	9.973	10.155	10.168	10.191	9.986			10.091	10.224
	B1B95	9.114	10.263	10.268	10.135	10.105	9.949	10.233	10.231	10.247	10.121			10.200	10.264		10.188
	B3LYP	9.020	10.263	10.263	10.151	10.094	10.107	10.258	10.272	10.292	10.112			10.207	10.319		10.285	10.333
	B3LYPultrafine					10.093
	B3PW91	9.092	10.332	10.332	10.190	10.130	10.143	10.256	10.270	10.288	10.140			10.218	10.301
	mPW1PW91	9.036	10.290	10.290	10.145	10.081	10.092	10.210	10.215	10.233	10.087			10.171	10.248
	M06-2X											10.250
	PBEPBE	9.083	10.311	10.311	10.199	10.142	10.156	10.306	10.310	10.330	10.161			10.257	10.358
	TPSSh					9.961
	B97D3																			10.200
		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	cc-pVDZ	cc-pVTZ	cc-pVQZ	aug-cc-pVDZ	aug-cc-pVTZ	aug-cc-pVQZ	daug-cc-pVTZ
Moller Plesset perturbation	MP2	8.243	9.939	9.939	9.843	9.944	10.025	10.167	10.140	10.246	10.205			10.165	10.437		10.306	10.496
	MP2=FULL	8.245	9.942	9.942	9.845	9.958	10.039	10.179	10.154	10.259	10.226			10.175	10.467		10.316	10.523
	MP3					9.803		10.046
	MP3=FULL					9.814		10.022
	MP4		9.983			9.955				10.237
	B2PLYP=FULLultrafine					9.967												10.292
Configuration interaction	CID		9.743	9.743	9.621	9.625			9.769
	CISD			9.766	9.647	9.642			9.785
		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	cc-pVDZ	cc-pVTZ	cc-pVQZ	aug-cc-pVDZ	aug-cc-pVTZ	aug-cc-pVQZ	daug-cc-pVTZ
Quadratic configuration interaction	QCISD		9.951	9.951	9.845	9.869	9.939	10.055	10.023	10.113	10.065			10.045	10.250
	QCISD(T)					9.966								10.154	10.403
Coupled Cluster	CCD		9.915	9.915	9.806	9.821	9.897	10.011	9.978	10.072	10.029			10.008	10.218		10.122
	CCSD(T)					9.962								10.151	10.400		10.282	10.450
	CCSD(T)=FULL					9.974									10.420		10.284
		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	cc-pVDZ	cc-pVTZ	cc-pVQZ	aug-cc-pVDZ	aug-cc-pVTZ	aug-cc-pVQZ	daug-cc-pVTZ

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Ionization Energies in eV

Methods with effective core potentials (select basis sets)

		CEP-31G	CEP-31G*	CEP-121G	CEP-121G*	LANL2DZ	SDD	cc-pVTZ-PP	aug-cc-pVTZ-PP	Def2TZVPP
hartree fock	HF	8.620	8.520	8.759	8.682	8.819	8.823			8.750
density functional	B3LYP	9.950	9.884	10.112	10.067	10.218	10.212
Moller Plesset perturbation	MP2	9.687	9.813	9.899	10.017	9.940	9.946

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.