RELATIVE STABILITY OF HEXAGONAL AND PLANAR STRUCTURES OF HYPOTHETICAL C3N4 SOLIDS

We have performed a first-principles electronic-structure study of a planar structural form of a hypothetical C3N4 solid and compared its energy to a fully three-dimensional form. We use a mixed basis of pseudoatomic orbitals and low-kinetic-energy plane waves to determine the single-particle Kohn-Sham wave functions. These results are tested against fully converged plane-wave-basis calculations. We find that the proposed planar form of C3N4 (p-C3N4) is lower in energy than the hexagonal form -C3N4. However, the energy difference between the two phases is small. The hexagonal -C3N4 phase is insulating, with an indirect gap, while the planar form p-C3N4 has a semimetallic electronic structure. © 1995 The American Physical Society.