Table 2.

Calculated tetrad stacking energies (kcal/mol) of experimentally observed stacking modes

Stacking mode	MP2 6-31G*(0.25)a		MP2 6-311 + G(2d,2p)		AMBER
	ΔE	ΔEnorm	ΔE	ΔEnorm	EAmber
Core
Partial 5/6-ring	−153.56	5.74	−157.37	4.21	2.07
5-ring	−150.74	8.56	−153.77	7.81	3.64
Partial 6-ring	−147.71	11.59	−149.70	11.88	10.09
Interface
Partial 6-ring	−147.78	11.52	−149.90	11.69	9.24
6-ring	−153.72	5.58	−156.71	4.88	5.27
5/6-ring	−157.66	1.64	−161.58	0.00	2.29
5-ring	−149.99	9.31	−152.45	9.14	4.76

Rotation and separation coordinates corresponding to these energies are the averages presented in Table 1.

^aEnergies determined by interpolation from available data on the energy landscapes of the same- and opposite-polarity stacked tetrads.