Impact-formed complex diamond-graphite nanostructures

Shock waves resulting from asteroidal and laboratory impacts convert sp2-bonded graphitic material to sp3-bonded diamond. Depending on the shock pressure and temperature conditions, complex nanostructures can form that are neither graphite nor diamond but belong to the diaphite material group, which are characterized by structurally intergrown layered sp2- and sp3-bonded carbon domains. Our ultrahigh-resolution transmission electron microscopy images combined with density functional theory calculations demonstrate that diaphites have two related but distinct structural families. Here, we describe diaphite nanostructures from natural and laboratory shocked samples, provide a framework for classifying the members of these materials, and draw attention to their excellent mechanical and electronic material properties.