  Molecular dynamics simulation is used to study thermally activated migration
of hydrogen atoms in graphone, a magnetic semiconductor formed of a graphene
monolayer with one side covered with hydrogen so that hydrogen atoms are
adsorbed on each other carbon atom only. The temperature dependence of the
characteristic time of disordering of graphone via hopping of hydrogen atoms to
neighboring carbon atoms is established directly. The activation energy of this
process is found to be Ea=(0.05+-0.01) eV. The small value of Ea points to
extremely low thermal stability of graphone, this being a serious handicap for
practical use of the material in nanoelectronics.
