Table 4. Mean Absolute Errors in Calculated Heats of Formation (kcal/mol) and Relative Energies (kcal/mol) for the G2G3-CHNOF Benchmark Set: MNDO, AM1, PMx, and OMx.

		method
subset	N	MNDO	AM1	PM3	PM6	PM7	OM1	OM2	OM3
Heats of Formation
G2	93	7.71	7.44	6.86	5.69	5.14	4.64	3.37	3.83
G3	52	7.51	6.73	5.01	3.86	3.40	4.25	3.18	3.71
alkanes28	22	3.26	8.81	2.03	4.20	1.76	2.16	1.91	0.72
Relative Energies
alkanes28	6	6.16	4.35	1.76	1.05	1.51	4.68	0.61	1.48