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 C₃ (carbon trimer)

Experimental Ionization Energy is 13 ± 0.1 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	11.812
	G3	11.823
	G3B3	12.284
	G4	12.326
	CBS-Q	11.792

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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	10.453	12.658	12.658	12.491								11.728							11.585
density functional	LSDA	10.190	12.124	12.124	11.968	12.073	12.073	12.296	12.319	12.319	12.118			12.239	12.318
	BLYP	9.577	11.405	11.405	11.263	11.349	11.349	11.611	11.592	11.592	11.403			11.523	11.617
	B1B95	10.358	12.158	12.158	11.976	12.048	12.048	12.232	12.235	12.235	12.074			12.191	12.227
	B3LYP		12.920	12.920	12.262	12.208	12.208	12.407	12.393	12.393	12.243		12.419	12.354	12.404	12.410		12.421	12.415
	B3LYPultrafine					12.208												12.421
	B3PW91	10.417	12.249	12.249	12.040	12.103	12.103	12.273	12.285	12.285	12.123			12.240	12.277
	mPW1PW91	10.331	12.245	12.245	12.046	12.122	12.122	12.300	12.302	12.302	12.137			12.257	12.295
	M06-2X			12.738		12.386						11.596
	PBEPBE	9.669	11.539	11.539	11.363	11.446	11.446	11.669	11.649	11.647	11.479			11.601	11.671
	PBE1PBE					12.076
	HSEh1PBE		12.176			12.056		12.239							12.247
	TPSSh					11.961		12.119			11.978				12.123
	wB97X-D			12.870		11.516		11.687		11.690			11.722	11.697	11.640			11.643
	B97D3		12.659			11.404		11.604		11.584		11.595	11.656		11.600			11.610		11.614
		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	8.086	10.681		10.486	11.041	10.816	10.884	11.287	11.073	11.058		11.060	11.020	11.262		11.166	11.312
	MP2=FULL	8.085	10.682		10.487	10.822	10.822	11.042	11.082	11.082	11.069			11.023	11.277			11.327
	MP4					17.051				15.596					17.623
	B2PLYP					11.575									11.938
	B2PLYP=FULLultrafine					11.636								11.825	11.893			11.911
Configuration interaction	CID		11.488		11.357	11.892			12.317
	CISD		11.371		11.236	11.795			12.210
Quadratic configuration interaction	QCISD(T)					13.693								13.912	14.140
Coupled Cluster	CCD		11.236			11.726	11.726		12.179	12.179	12.193			12.106	12.234
	CCSD(T)													13.937
	CCSD(T)=FULL					13.669
		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	12.576	12.628	12.585	12.674	12.640	12.637			11.573
density functional	B3LYP	12.199	12.230	12.220	12.282	12.440	12.427			11.849
	PBEPBE									11.682
Moller Plesset perturbation	MP2	10.658	10.970	10.714	11.027	10.665	10.666			11.465

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.