Optical properties of graphite and boron nitride

The energy bands of graphite and boron nitride have been calculated using the tight-binding approximation, with atomic potentials obtained by the SCF CNDO method. On the basis of the calculated bands some optical properties of the above materials are discussed. The optical absorption of the hot-pressed pyrolitic boron nitride was measured in the wavelength region from 25000 to 50000 cm -1 and the width of the forbidden gap was found to be 4.3 eV. Comparisons with the previous calculations have also been made.