Table II.

Hydrogen bond complex energies from ωB97X/6-31G* and model errors (kcal/mol) for the artificially expanded genetic information system (AEGIS) base pair dataset^77,85,86 with Leontis and Westhof symbols used for the classification of nucleic acid base pairs,^139–141 including complexes that involve alternative tautomers and protonation states.^a

		QM/Δ-MLP or MLP			DFTB			NDDO
	ωB97X	QDπ	AIQM1	ANI-2x	GFN2	DFTB3	ChIMES	ODM2	D3H4X	PM7
Complex	ΔE	Err	Err	Err	Err	Err	Err	Err	Err	Err
	‒32.90	0.16	7.75	9.84	3.66	10.98	0.08	10.35	4.87	1.92
	‒18.22	‒0.14	6.71	3.65	2.15	9.33	2.19	7.51	2.90	0.88
	‒18.36	0.17	7.39	3.39	2.12	9.35	2.22	7.45	2.94	0.96
	‒37.40	0.03	10.01	7.67	3.99	11.34	‒0.64	10.18	6.62	3.80
	‒34.52	‒0.00	9.70	8.04	2.43	9.32	‒2.73	8.57	5.25	1.83
	‒22.46	‒0.08	7.06	6.34	2.13	9.56	1.99	9.14	1.69	‒1.24
	‒33.11	‒0.05	8.13	10.77	3.65	10.14	‒0.76	10.93	5.50	1.83
	‒32.50	‒0.31	8.20	8.38	3.72	10.21	‒0.69	10.13	5.28	1.28
	‒33.68	0.13	7.45	10.02	4.56	11.02	‒0.56	11.61	6.47	1.77
	‒22.46	0.09	8.76	9.08	3.56	10.54	3.50	9.95	4.24	‒0.24
	‒33.99	0.03	7.28	10.79	4.59	10.11	‒3.34	9.56	5.51	3.22
	‒23.00	0.39	7.82	7.14	3.03	9.49	‒0.04	8.55	0.41	‒0.67
	‒25.59	‒0.11	8.99	13.00	3.14	10.75	‒2.45	8.60	1.71	‒3.49
	‒22.92	‒0.03	5.80	6.18	3.04	9.44	0.24	8.88	0.43	‒0.08
	‒144.48	0.10	12.53	79.73	14.30	18.59	8.26	15.79	15.52	15.29
	‒43.33	‒0.07	12.36	11.58	6.69	15.35	3.42	12.16	4.25	1.90
	‒47.17	0.04	6.77	24.45	3.38	13.41	0.87	9.41	7.35	4.82
maE	…	0.11	8.46	14.17	4.25	11.22	1.99	10.08	4.87	2.77
rmsE	…	0.15	8.66	22.51	5.09	11.49	2.83	10.26	5.97	4.44

^a Models and datasets are described in Sec. II. An illustration of each of the complexes is provided in Fig. 4. Complexes include adenine (A), cytosine (C), guanine (G), thymine (T), uracil (U), isoguanine (B), isocytosine (S), 6-amino-5-nitropyridin-2-one (Z), 2-aminoimidazo[1,2a][1,3,5]triazin-4(1H)-one (P), imidazo[1,2-a]-1,3,5-triazine-2(8H)-4(3H)-dione (X), 2,4-diaminopyrimidine (K), 4-aminoimidazo[1,2-a][1,3,5]triazin-2(8H)-one (J), and 6-amino-3-methylpyridin-2(1H)-one (V).^86,142 The “*” symbol refers to tautomeric form, and the “+” and “−” symbols refer to the positive and negative charge.