Adsorption of gaseous species, and in particular of hydrogen atoms, on graphene is an important process for the chemistry of this material. At the equilibrium geometry, the H atom is covalently bonded to a carbon that puckers out from the surface plane. Nevertheless the flat graphene geometry becomes important when considering the full sticking dynamics. Here we show that GGA-DFT predicts the wrong spin state for this geometry, namely, S-z = 0 for a single H atom on graphene. We show that this is caused by fractional electron occupations in the two bands closest to the Fermi energy, an effect of the self-interaction error. It is also demonstrated that the use of hybrid functionals or the GGA+U method can be used to retrieve the correct spin solution although the latter gives an incorrect potential energy curve.

Role of the self-interaction error in studying chemisorption on graphene from first-principles / S. Casolo, E. Flage-Larsen, O.M. Løvvik, G.R. Darling, G.F. Tantardini. - In: PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS. - ISSN 1098-0121. - 81:20, art. numb. 205412(2010 May 15).

Role of the self-interaction error in studying chemisorption on graphene from first-principles

S. Casolo
Primo
;
G.F. Tantardini
Ultimo
2010-05-15

Abstract

Adsorption of gaseous species, and in particular of hydrogen atoms, on graphene is an important process for the chemistry of this material. At the equilibrium geometry, the H atom is covalently bonded to a carbon that puckers out from the surface plane. Nevertheless the flat graphene geometry becomes important when considering the full sticking dynamics. Here we show that GGA-DFT predicts the wrong spin state for this geometry, namely, S-z = 0 for a single H atom on graphene. We show that this is caused by fractional electron occupations in the two bands closest to the Fermi energy, an effect of the self-interaction error. It is also demonstrated that the use of hybrid functionals or the GGA+U method can be used to retrieve the correct spin solution although the latter gives an incorrect potential energy curve.
Density-functional theory ; augmented-wave method ; pair-density ; model ; hydrogen ; surface ; energy ; adsorption ; graphite ; systems
Settore CHIM/02 - Chimica Fisica
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/154600
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