Table 1.

DFTB versus DFT relative energies (eV) of several isomers and dissociation fragments of , and . Only the lowest spin multiplicities were considered.

species		DFT	DFTB	species		DFT	DFTB
C
naphthalene	(a)	0.0	0.0	pyrene	(a)	0.0	0.0
azulene	(b)	0.81	1.0	vinylidene	(b)	1.45	1.45
benzofulvene	(c)	0.97	1.02	H-shifted	(c)	2.62	2.64
				ethynyl	(d)	2.83	2.82
	(d)	5.20	5.48
	(e)	5.28	5.58		(e)	5.49	5.95
	(f)	4.61	5.81		(f)	5.68	6.00
	(g)	4.66	5.89		(g)	5.74	6.02
	(h)	4.84	5.64		(h)	4.48	5.65
	(i)	4.38	4.76		(i)	4.54	5.74
					(j)	7.08	7.65
C
coronene	(a)	0.0	0.0
vinylidene	(b)	1.30	1.46
H-shifted	(c)	2.35	2.51
ethynyl	(d)	2.48	2.52
	(e)	5.59	5.99
	(f)	4.40	5.58
	(g)	7.43	7.96