National Institute of Standards and Technology

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

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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 HCN (Hydrogen cyanide)

Experimental Ionization Energy is 13.6 ± 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.

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Ionization Energies in eV

Methods with predefined basis sets

semi-empirical	AM1
composite	G2	13.580
	G3	13.579
	G3B3	13.567
	G4	13.555
	CBS-Q	13.598

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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	10.801	12.242	12.242	12.120	11.898	11.892	11.958	11.979	11.980	11.844	11.954	12.010	11.887	11.935	11.946	11.898	11.940	11.945	11.935	11.940
density functional	LSDA	13.458			14.591
	BLYP	11.873	13.608	13.608	13.234	13.086	13.087	13.262	13.243	13.248	13.080			13.116	13.258		13.261			13.258
	B1B95	12.296	13.539	13.540	13.487	13.276	13.381	13.440	13.461	13.463	13.313	13.415	13.441	13.342	13.388		13.358			13.331
	B3LYP	12.164	13.479	13.479	13.424	13.290	13.291	13.428	13.456	13.461	13.277	13.486	13.505	13.311	13.458	13.481	13.417	13.477	13.485	13.458
	B3LYPultrafine					13.290	13.291	13.428	13.456		13.277	13.487	13.505	13.312	13.458		13.417	13.477
	B3PW91	12.259	13.566	13.566	13.474	13.327	13.327	13.424	13.455	13.458	13.302	13.463	13.488	13.335	13.439		13.396	13.453		13.439
	mPW1PW91	12.225	13.527	13.527	13.429	13.257	13.256	13.358	13.378	13.402	13.251	13.411	13.442	13.265	13.366		13.348	13.403		13.366
	M06-2X	12.318	13.649	13.647	13.587	13.375	13.370	13.468	13.520	13.522	13.365	13.527	13.539	13.386	13.512		13.450	13.523
	PBEPBE	12.835	13.759	13.759	13.686	13.220	13.222	13.359	13.378	13.381	13.204	13.414		13.244	13.384					13.381
	PBEPBEultrafine		13.767
	PBE1PBE	12.187				13.259	13.259	13.361	13.379	13.382	13.233	13.392	13.423	13.270	13.370		13.333	13.386
	HSEh1PBE	12.166				13.244	13.243	13.347	13.369	13.372	13.217	13.381	13.412	13.253	13.361		13.319	13.376
	TPSSh	12.107				13.165	13.164	13.266	13.284	13.286	13.137	13.297	13.329	13.167	13.281	13.298	13.233	13.299	13.303
	wB97X-D	12.177	13.602	13.602	13.498	13.301	13.302	13.397	13.422	13.424	13.271	13.422	13.449	13.438	13.388	13.415	13.357	13.402	13.418
	B97D3	12.073																			13.302
		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				13.739	13.622	13.650	13.763	13.758	13.788	13.803	13.974	13.798	13.696	13.942	14.035	13.841	13.997	14.062	13.942
	MP2=FULL					13.630	13.659	13.772	13.770	13.799	13.817	13.993	13.809	13.702	13.964	14.058	13.847	14.021	14.084	13.964
	MP3					13.094		13.067				13.425	13.242	13.161	13.397
	MP3=FULL					13.102	13.130	13.221	13.221	13.250	13.323	13.447	13.253	13.167	13.425		13.296	13.484
	MP4					13.359				13.547		13.756	13.560	13.422	13.724		13.566	13.777
	MP4=FULL					13.369				13.575		13.786		13.429	13.751		13.575	13.803
	B2PLYP				13.393	13.270	13.277	13.402	13.422	13.434	13.326	13.520	13.472	13.301	13.487		13.413	13.518
	B2PLYP=FULL				13.394	13.274	13.281	13.406	13.426	13.438	13.335	13.529	13.477	13.303	13.498		13.416	13.531
	B2PLYP=FULLultrafine				13.394	13.274	13.281	13.406	13.426	13.438	13.335	13.529	13.477	13.304	13.498		13.416	13.531
Configuration interaction	CID		13.055	13.055	13.134	12.951			13.065			13.222		12.997	13.198
	CISD		12.971	12.971	12.955	12.910			13.031			13.201		12.949	13.175
		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		13.073	13.073	13.030	13.029	13.056	13.150	13.164	13.190	13.241	13.396	13.208	13.078	13.363		13.201	13.409		13.363
	QCISD(T)					13.162			13.303			13.593	13.335	13.222	13.574		13.411	13.635		13.574
	QCISD(T)=FULL					13.169		13.303				13.604		13.226	13.570	13.686	13.408	13.613
	QCISD(TQ)					13.149		13.247						13.219	13.581	13.663	13.451	13.770
	QCISD(TQ)=FULL					13.156		13.295				13.589		13.222	13.574	13.676		13.637
Coupled Cluster	CCD					13.145	13.169	13.261	13.263	13.289	13.315	13.452	13.298	13.200	13.425		13.320	13.470
	CCSD					12.998	13.015	13.105	13.122	13.147	13.193	13.346	13.168	13.033	13.313	13.404	13.146	13.358	13.421
	CCSD=FULL					13.005					13.225	13.378	13.180	13.042	13.353	13.442	13.160	13.405	13.459
	CCSD(T)					13.072	13.097	13.195	13.213	13.239	13.302	13.471	13.261	13.120	13.440	13.533	13.254	13.485	13.562	13.433
	CCSD(T)=FULL					13.085						13.501	13.269	13.129	13.480	13.578	13.268	13.530	13.588
		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	12.026	11.780	12.057	11.906	12.110	12.108			11.946
density functional	B1B95									13.404
	B3LYP	13.303	13.112	13.358	13.218	13.491	13.471			13.471
	B3LYPultrafine									13.471
	B3PW91									13.449
	mPW1PW91									13.400
	M06-2X									13.503
	PBE1PBE									13.382
	HSEh1PBE									13.371
	TPSSh									13.291
	wB97X-D	13.328	13.103	13.368	13.214	13.507	13.494			13.410
Moller Plesset perturbation	MP2		13.571		13.653					13.961
	MP2=FULL									13.977
	MP3									13.415
	MP3=FULL									13.433
	MP4									13.740
	MP4=FULL									13.752
	B2PLYP									13.503
	B2PLYP=FULL									13.511
	B2PLYP=FULLultrafine									13.511
Configuration interaction	CID									13.213
	CISD									13.190
Quadratic configuration interaction	QCISD									13.379
	QCISD(T)									13.570
	QCISD(T)=FULL									13.580
	QCISD(TQ)									13.565
	QCISD(TQ)=FULL									13.529
Coupled Cluster	CCD									13.439
	CCSD									13.331
	CCSD=FULL									13.358
	CCSD(T)									13.448
	CCSD(T)=FULL									13.478

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.