2013/12/26 by Casartelli, M., Casolo, S., Tantardini, G. F. +1
#FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci)
paper · doi:10.48550/arxiv.1312.7143
Adsorption of hydrogen atoms to a carbon atom vacancy in graphene is investigated by means of periodic first principles calculations, up to the fully hydrogenated state where six H atoms chemically bind to the vacancy. Addition of a single H atom is highly exothermic and barrierless, and binding energies remain substantial for further hydrogenation, with a preference towards structures with the least number of geminal pairs. Thermodynamic analysis shows that defective graphene is extremely sensitive to hydrogenation, with the triply hydrogenated anti- structure prevailing at room temperature and for a wide range of H2 partial pressures, from ∼1 bar down to <10-20 bar. This structure has one unpaired electron and provides a spin-half local magnetic moment contribution to graphene paramagnetism. Comparison of our results with recent TEM, STM and μ-SR experiments suggest that carbon atom vacancies may actually be hydrogenated to various degrees under varying conditions.