CALCULATION OF THE GROUND-STATE PROPERTIES OF DIAMOND AND CUBIC BORON-NITRIDE

Using the modified augmented plane wave method (MAPW), the ground stat e properties of cubic boron nitride and diamond are investigated withi n the framework of the local density approximation (LDA). As is common for LDA, the value of the band gap is underestimated by the one-parti cle excited states: Calculation of the total energy as a function of t he lattice parameter yields equilibrium lattice constants within 1% of the experimental value. Furthermore, the hydrostatic bulk moduli obta ined deviate from the experimental values by about 10% in the case of BN and 4% in the case of diamond. An estimate of the cohesion energy o f both materials is obtained from the atomic limit within the MAPW sch eme yielding improved values when compared to the difference between c rystal and single atom LDA total energies.