Band Structure and Interband Optical Absorption in Diamond

In the present paper we compute the interband contribution to the imaginary part ${\epsilon }_2\left(\omega \right)$ of the dielectric constant in diamond. This is done for several model band structures. In particular, we conclude that either the present first-principles calculations have to be modified or there are extremely large many-particle corrections to the interband current near the fundamental ultraviolet absorption edge.