First-principles studies of structural and electronic properties of hexagonal BC5

Structural and electronic properties for seven possible stacking configurations in hexagonal BC5 based on hexagonal BN and graphite structures have been studied using the ab initio pseudopotential density functional method within the local density approximation. From the total energies, structural parameters, and electron density of states calculated after full structural relaxation, the configuration BC5-I with AA stacking sequence along the c axis based on the hexagonal BN structure has been shown to be the most stable structure among the seven possible stacking configurations, and both the monolayer and bulk phases of BC5 are expected to show metallicity. The structural stability of BC5-I has been confirmed by calculations of the elastic constants and phonon frequencies.