An APW calculation of the energy band in diamond using different approximations for the exchange energy

The valence and conduction bands of diamond were calculated by the augmented plane wave (APW) method for the points of higher symmetry of the Brillouin zone. The calculations were carried out for four different approximations to the exchange energy. The convergence of the method was studied, and a limited study of the self- consistency in the potential was made. Very good results were obtained using a non-muffin-tin potential between APW spheres, instead of a constant. The correlation effects appear to be of importance, and very good results were obtained making an approximate self- consistency in the dielectric constant. On the other hand, self-consistency in the crystal potential was shown to be of minor importance for diamond.