Table 5.

Interaction energy (kcal mol⁻¹) between stacked DNA base pairs in terms of the additivity scheme, computed at KT1/TZ2P^a,b

System	TW	ΔEAC	ΔEBD	ΔEAD	ΔEBC	ΔEadd	ΔEcoop	ΔEint
AT-AT	0	−1.23	+1.26	−1.24	−1.24	−2.45	+1.04	−1.41
AT-AT	36	−5.27	−3.93	−1.11	−0.93	−11.24	+1.11	−10.13
AT-AT	180	−1.84	+0.39	−5.44	−5.44	−12.33	+1.62	−10.71
AU-AU	0	−1.23	+0.94	−1.37	−1.37	−3.03	+1.17	−1.86
AU-AU	36	−5.27	−3.00	−1.20	−1.08	−10.55	+1.20	−9.35
AU-AU	180	−1.84	+0.28	−4.67	−4.67	−10.90	+1.73	−9.17
GC-GC	0	+2.15	+2.83	−4.90	−4.90	−4.82	+4.42	−0.40
GC-GC	36	−2.08	−1.32	−3.44	−4.71	−11.55	+3.92	−7.63
GC-GC	180	−7.59	−2.60	−1.52	−1.52	−13.23	+1.98	−11.25

^aSee Scheme 6:

^bPost-SCF on LDA/TZ2P orbitals / densities.