  We show by means of molecular dynamics simulations that graphene is an
excellent coating for diamond. The transformation of diamond to amorphous
carbon while sliding under pressure can be prevented by having at least two
graphene layers between the diamond slabs, making this combination of materials
suitable for new coatings and micro- and nanoelectromechanical devices. Grain
boundaries, vacancies and adatoms on the diamond surface do not change this
picture whereas reactive adsorbates between the graphene layers may have
detrimental effects. Our findings can be explained by the properties of layered
materials where the weak interlayer bonding evolves to a strong interlayer
repulsion under pressure.
