Lattice dynamics of a layered material BC 2N

Vibrational properties of new layered compounds BC ₂N are investigated based on a generalized valence-force field model whose force constants have been determined from ab initio total energy calculation. The calculated phonon density-of-states spectra in the higher-energy region show different peak structures depending on local atomic arrangements. If crystal structures of BC ₂N have patterns segregated into graphite and hexagonal boron nitride and each segregated domain contains more than dozens of atoms, the phonon spectra of these structures can be described by a superposition of the spectra of graphite and hexagonal boron nitride. There is a possibility of determining polymorphic structures of BC ₂N from the lattice vibrations.