PROPERTIES OF B2O - AN UNSYMMETRICAL ANALOG OF CARBON

The compound B2O has been proposed to be an isoelectronic analog of ca rbon. The high-temperature, high-pressure syntheses of both ''graphite like'' and ''diamondlike'' phases of B2O have been reported, although the material has not been well characterized. We have applied the dens ity-functional total-energy method to two candidate structures for thi s material. Both structures are based on a diamond lattice, but differ in the direction of stacking of the boron and oxygen planes. In order to find the equilibrium structures, we have relaxed both the internal coordinates and the unit-cell parameters. We find that one structure, proposed previously, is unstable, while the other has a bulk modulus of approximately 2 Mbar, comparable to SiC.