Adsorption energies and surface–adsorbate bond distances for carboxylic acid, amide and ester adsorbates on the α-Al₂O₃(0001) surface.

Adsorbate	Adsorption configuration	Adsorption energy/eV	Surface–adsorbate bond distance/Å
			Al–O	Al–N	O–H	O⋯H
Formic acid	Molecular, bound via carbonyl O	−1.42	1.92			2.23
	Molecular, bound via hydroxyl O	−0.95	2.01			2.34
	Dissociated	−1.80	1.76
	Dissociated hydrogen-bonded	−2.33	1.81		1.04	1.58
Formamide	Molecular, bound via O	−1.64	1.87
	Molecular, bound via N	−1.16		2.04
	Dissociated, bound via N	−1.22		1.85	0.98
	Dissociated hydrogen-bonded	−1.85		1.89	1.08	1.45
Methyl formate	Molecular, bound via carbonyl O	−1.54	1.91			2.13
	Molecular, bound via ether O	−1.06	2.00
Oxalic acid	Molecular, bound via hydroxyl O	−1.03	2.02
	Bridge, bound via carbonyl O and hydrogen bond	−1.63	1.85		1.09	1.36
	Dissociated hydrogen-bonded	−2.09	1.80		1.02	1.71
	Dissociated hydrogen-bonded bridge, bound via two carbonyl O	−2.69	1.85, 1.95		0.99	2.00