Density functional theory study of hydrogen adsorption on Fe(sub 5)C(sub 2)(001), Fe(sub 5)C(sub 2)(110), and Fe(sub 5)C(sub 2)(100)

Density functional theory calculation was carried out for hydrogen adsorption on the (001), (110), and (100) surfaces of Fe(sub 5)C(sub 2) and found that the most stable hydrogen species is C(sub S)H at 1/3 and 2/3 monolayer (ML) on (001). On the metallic Fe(Sub 5)C(sub 2)(100) surface which lacks surface carbon atoms on the surface monolayer, dissociated hydrogen is found at 1/2 ML, while both dissociated hydrogen and activated H(sub 2) are found at 1 ML.