Table 3.

Report of calculated adsorption energies (in kcal mol⁻¹) for the interaction of nucleobases with Na⁺-montmorollinite [124] and H⁺-montmorollinite [126]. Perpendicular and parallel adsorptions with respect to the external surface are indicated as ┴ and ║, respectively.

External Surface	Nucleobase	Adsorption Type	ΔEads
Na+-free side	Adenine	┴	−3.7
		║	−10.8
	Cytosine	┴	−6.6
		║	−9.1
	Guanine	┴	−11.3
		║	−10.9
	Thymine	┴	−7.3
		║	−10.7
	Uracil	┴	−5.7
		║	−8.5
Na+-containing side	Adenine	Cation–π/ring	−11.6
		Cation–π/displaced	−17.0
		Cation–heteroatom	−20.2
	Cytosine	Cation–π/ring	−10.2
		Cation–π/displaced	−26.6
		Cation–heteroatom	−27.0
	Guanine	Cation–π/ring	−13.1
		Cation–π/displaced	−26.1
		Cation-heteroatom	−27.6
	Thymine	Cation–π/ring	−7.6
		Cation–π/displaced	−21.7
		Cation–heteroatom	−19.1
	Uracil	Cation–π/ring	−5.7
		Cation–π/displaced	−21.2
		Cation–heteroatom	−18.8
H+-montmorillonite	Adenine	║ on tetrahedral substituted	−37.7
		║ on octahedral substituted	−49.1
		┴ on tetrahedral substituted	−39.0
		┴ on octahedral substituted	−49.4
	Guanine	║ on tetrahedral substituted	−39.8
		║ on octahedral substituted	−48.4
		┴ on tetrahedral substituted	−40.7
		┴ on octahedral substituted	−50.0
	Cytosine	║ on tetrahedral substituted	−42.4
		║ on octahedral substituted	−44.0
		┴ on tetrahedral substituted	−32.3
		┴ on octahedral substituted	−41.8