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 Li₂ (Lithium diatomic)

Experimental Ionization Energy is 5.1127 ± 0.0003 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	5.208
	G3	5.204
	G3B3	5.209
	G4	5.119
	CBS-Q	5.111

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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	cc-pV(T+d)Z	daug-cc-pVTZ
hartree fock	HF	3.601	4.217	4.217	4.208	4.191	4.191	4.208	4.247	4.247	4.170		4.305	4.211	4.232	4.230	4.218	4.231	4.230	4.232	4.231
density functional	BLYP					5.150
	B1B95	4.538	4.995	4.995	5.032	5.031	5.031	5.038	5.024	5.024	5.009			5.024
	B3LYP	4.776	5.237	5.237	5.251	5.236	5.236	5.245	5.241	5.241	5.222		5.276	5.237	5.227	5.229	5.236	5.228	5.228	5.227
	B3LYPultrafine					5.236												5.228
	mPW1PW91	4.582	5.085	5.085	5.104	5.090	5.090	5.096	5.104	5.104	5.077			5.091	5.091					5.091
	M06-2X			5.326		5.334						5.321
	PBEPBE	4.684	5.153	5.153	5.181	5.169	5.169	5.175	5.169	5.169	5.157			5.164	5.157					5.157
	PBE1PBE					5.103
	HSEh1PBE		5.087			5.102									5.100
	TPSSh					5.173		5.178			5.160				5.170
	wB97X-D			4.997		4.971		4.977		5.008			5.075	4.977	5.005			5.002
	B97D3		5.118			5.077		5.085		5.102		5.095	5.180		5.091			5.085			5.085
		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	cc-pV(T+d)Z	daug-cc-pVTZ
Moller Plesset perturbation	MP2	4.034	4.639	4.639	4.671	4.699	4.709	4.710	4.758	4.758	4.753			4.799	4.900		4.750	4.925	4.832	4.900
	MP2=FULL	4.041	4.648	4.648	4.637	4.702	4.702	4.716	4.770	4.770	4.774			4.738	4.823	4.885			4.887	4.823
	MP3=FULL					4.871		4.883
	MP4		4.883			4.938				4.996					5.022
	B2PLYP=FULLultrafine					5.049								5.065	5.084			5.087
		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	cc-pV(T+d)Z	daug-cc-pVTZ
Quadratic configuration interaction	QCISD		4.947	4.947	4.937	4.998	4.998	5.009	5.060	5.060	5.031			5.043	5.089					5.089
Coupled Cluster	CCD		4.941	4.941	4.929	4.996	4.996	5.006	5.057	5.057	5.028			5.040	5.084		5.049	5.085
	CCSD(T)=FULL					5.004										5.158			5.155
		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	cc-pV(T+d)Z	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	4.116	4.086	4.297	4.257	4.238	4.253			4.285
density functional	B3LYP	4.960	4.933	5.115	5.084	5.252	5.240			5.277
	PBEPBE									5.209
Moller Plesset perturbation	MP2	4.575	4.602	4.773	4.768	4.650	4.728

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.