The atomic models of diamondlike allotropes of crystalline C40 hyperdiamond, hyperlonsdaleite and socalled autointercalated hyperdiamond are offered and using the density-functional based tight-binding method their structural, cohesive, elastic, and electronic properties are predicted as well as their theoretical x-ray diffraction spectra are derived. Among these allotropes the autointercalated hyperdiamond C40 has a unique combined type of both covalent and van der Waals bonding and shows the highest density and hardness.
http://dx.doi.org/10.1103/PhysRevB.77.113402