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 PO₂ (Phosphorus dioxide)

Experimental Ionization Energy is 11.9 ± 0.5 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

semi-empirical	PM3
composite	G2	10.676
	G4	10.828

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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	daug-cc-pVTZ
hartree fock	HF		11.222	10.576	11.515	10.644	10.644	10.756	10.635	10.635	10.474		10.676	10.493	10.602	10.664	10.670	10.667	10.660
	ROHF		10.841	10.386	11.117	10.474	10.474	10.590	10.468	10.468	10.310			10.294	10.430		10.477	10.497
density functional	LSDA	7.792	11.144	10.916	11.530	11.117	11.117	11.319	11.166	11.166	10.970			10.906	11.153		11.198
	BLYP	7.264	10.482	10.242	10.899	10.481	10.482	10.716	10.529	10.529	10.319			10.263	10.517
	B1B95	7.911		10.723	11.475	10.725	10.860	11.025	10.894	10.894	10.687			10.685	10.703		10.779
	B3LYP	7.839	10.992	10.666	11.364	10.854	10.854	11.049	10.882	10.882	10.683		10.929	10.649	10.861		10.944	10.944
	B3LYPultrafine					10.854												10.944
	B3PW91	7.903	11.046	10.716	11.379	10.861	10.861	11.017	10.886	10.886	10.699			10.680	10.845
	mPW1PW91	8.040	11.060	10.749	11.430	10.854	10.854	11.011	10.875	10.910	10.725			10.668	10.829
	M06-2X			10.843		10.866						10.943
	PBEPBE	7.374	10.618	10.375	11.002	10.569	10.569	10.769	10.608	10.608	10.416			10.374	10.580
	PBE1PBE					10.840
	HSEh1PBE		11.041			10.838		10.999							10.819
	TPSSh					10.753		10.912			10.595				10.745
	wB97X-D			10.715		10.841		10.999		10.861			10.857	10.999	10.787			10.850
	B97D3		10.704			10.598		10.776		10.630		10.671	10.658		10.585			10.667	10.658
		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	daug-cc-pVTZ
Moller Plesset perturbation	MP2	5.376	9.599	9.493	10.003	10.029	10.029	10.234	9.993	9.993	10.084		10.094	9.750	10.226		10.215
	MP2=FULL		9.594	9.498	9.995	10.032	10.032	10.237	9.998	9.998				9.751	10.213
	MP3					10.495
	MP3=FULL					10.497
	MP4					9.884									10.154
	B2PLYP					10.489									10.559
	B2PLYP=FULLultrafine					10.490								10.262	10.555			10.655
Configuration interaction	CID			10.126		10.472			10.436
	CISD			10.083		10.447			10.412
		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	daug-cc-pVTZ
Quadratic configuration interaction	QCISD			9.934		10.321	10.321	10.514	10.289					10.100	10.547
	QCISD(T)					10.220
Coupled Cluster	CCD			9.997	10.707	10.397	10.397	10.581	10.360					10.166
	CCSD					10.377
	CCSD(T)														10.477
		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	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	11.584	10.687	11.454	10.655	11.793	11.628			10.656
density functional	B3LYP	11.550	10.942	11.426	10.926	11.619	11.465			10.938
	PBEPBE									10.659
Moller Plesset perturbation	MP2	10.104	10.069	9.992	10.068	10.174	10.126			10.341

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.